NUMBER05

index · ← NUMBER04 · NUMBER06 →
:: Elementary Number Theory Problems. {P}art {V}
::  by Artur Korni{\l}owicz and Adam Naumowicz
::
:: Received September 30, 2022
:: Copyright (c) 2022-2026 Association of Mizar Users
::           (Stowarzyszenie Uzytkownikow Mizara, Bialystok, Poland).
:: This code can be distributed under the GNU General Public Licence
:: version 3.0 or later, or the Creative Commons Attribution-ShareAlike
:: License version 3.0 or later, subject to the binding interpretation
:: detailed in file COPYING.interpretation.
:: See COPYING.GPL and COPYING.CC-BY-SA for the full text of these
:: licenses, or see http://www.gnu.org/licenses/gpl.html and
:: http://creativecommons.org/licenses/by-sa/3.0/.

environ

 vocabularies NUMBERS, SUBSET_1, ORDINAL1, ORDINAL2, CARD_1, XBOOLE_0, ARYTM_1,
      TARSKI, ARYTM_3, XXREAL_0, NAT_1, RELAT_1, INT_1, INT_2, SQUARE_1,
      NEWTON, FINSET_1, PBOOLE, FUNCT_1, ABIAN, FINSEQ_1, CARD_3, ORDINAL5,
      XCMPLX_0, ZFMISC_1, NUMBER05, NUMBER09;
 notations TARSKI, XBOOLE_0, SUBSET_1, RELAT_1, FUNCT_1, ORDINAL1, ORDINAL2,
      NUMBERS, ENUMSET1, XCMPLX_0, NAT_1, XXREAL_0, INT_1, INT_2, NAT_D,
      FINSEQ_1, MEMBERED, SQUARE_1, NEWTON, FINSET_1, PBOOLE, ABIAN, WSIERP_1,
      ORDINAL5;
 constructors NAT_D, RELSET_1, ABIAN, EULER_1, NAT_3, ORDINAL5, INT_5, PEPIN,
      DOMAIN_1, WSIERP_1, POLYEQ_3;
 registrations ORDINAL1, XXREAL_0, XREAL_0, NAT_1, CARD_1, INT_1, INT_2,
      WSIERP_1, FOMODEL0, ABIAN, VALUED_0, FINSET_1, MEMBERED, NEWTON02,
      ORDINAL5, NEWTON03, XCMPLX_0, NEWTON, NAT_6, PEPIN, RELAT_1;
 requirements REAL, NUMERALS, SUBSET, BOOLE, ARITHM;
 definitions MEMBERED, TARSKI, FUNCT_1, INT_2, NAT_D;
 equalities ORDINAL1, SQUARE_1;
 expansions INT_1, INT_2, ABIAN;
 theorems INT_1, INT_2, INT_5, XREAL_1, XXREAL_0, NEWTON03, TARSKI, NEWTON,
      WSIERP_1, FUNCT_1, PARTFUN1, PYTHTRIP, NAT_1, NEWTON01, GR_CY_3,
      POLYFORM, NAT_5, INT_6, EULER_2, NAT_4, EULER_1, PEPIN, XCMPLX_1,
      SERIES_2, FINSEQ_1, ORDINAL1, NAT_3, ABIAN, CARD_1, ZFMISC_1, XBOOLE_1,
      XBOOLE_0, NAT_D, ORDINAL5, SCHEME1, NAT_2, NUMBER02, HEYTING3, ENUMSET1,
      POLYEQ_3, SERIES_4, NEWTON05, POLYEQ_5, INT_4, XTUPLE_0, NUMBER03,
      XPRIMES0, XPRIMES1, SQUARE_1, LAGRA4SQ;
 schemes PBOOLE, NAT_1, SUBSET_1;

begin :: Problem 12

theorem Th1:
  for n,k being Nat st n|^|^k = 0 holds n = 0
  proof
    let n,k be Nat;
    assume A1: n|^|^k = 0;
    then k <> 0 by ORDINAL5:13;
    then consider j being Nat such that
    A2: k=j+1 by NAT_1:6;
    n|^|^(j+1) = n|^|^(Segm (j+1))
    .= n|^|^(succ Segm j) by NAT_1:38
    .= exp(n,n|^|^j) by ORDINAL5:14
    .= n|^(n|^|^j);
    hence n=0 by A1,A2;
  end;

registration
  let x be odd Nat;
  let i be Nat;
  cluster x|^|^i -> odd;
  coherence
  proof
    defpred P[Nat] means x|^|^$1 is odd;
    A1: P[0] by ORDINAL5:13,POLYFORM:4;
    A2:
    now
      let k be Nat;
      assume P[k];
      x|^|^(k+1) = x|^|^(Segm (k+1))
      .= x|^|^(succ Segm k) by NAT_1:38
      .= exp(x,x|^|^k) by ORDINAL5:14
      .= x|^(x|^|^k);
      hence P[k+1] by PEPIN:20;
    end;
    for k being Nat holds P[k] from NAT_1:sch 2(A1,A2);
    hence x|^|^i is odd;
  end;
end;

registration
  let x be non zero even Nat;
  let i be non zero Nat;
  cluster x|^|^i -> even;
  coherence
  proof
    consider j being Nat such that
    A1: i=j+1 by NAT_1:6;
    A2: x|^|^(j+1) = x|^|^(Segm (j+1))
    .= x|^|^(succ Segm j) by NAT_1:38
    .= exp(x,x|^|^j) by ORDINAL5:14
    .= x|^(x|^|^j);
    per cases;
    suppose x|^|^j > 0;
      hence x|^|^i is even by A2,A1;
    end;
    suppose x|^|^j = 0;
      hence thesis by Th1;
    end;
  end;
end;

:: Problem 12
theorem
  for n being non zero Nat ex x being non zero Nat st
  for i being Nat holds n divides x|^|^(i+1) + 1
  proof
    let n be non zero Nat;
    A1: n divides 2*n & 2 divides 2*n;
    set x=2*n-1;
    reconsider x as non zero odd Nat;
    take x;
    let i be Nat;

    A3: x|^|^((i)+1) = x|^|^(Segm((i)+1))
    .= x|^|^(succ Segm(i)) by NAT_1:38
    .= exp(x,x|^|^(i)) by ORDINAL5:14
    .= x|^(x|^|^(i));

    2*n divides x - -1; then
    x|^(x|^|^(i)), (-1)|^(x|^|^(i)) are_congruent_mod 2*n
    by GR_CY_3:34,INT_1:def 4;
    then x|^|^(i+1),-1 are_congruent_mod 2*n by A3;
    hence thesis by A1,INT_2:9;
  end;

begin :: Problem 13

theorem Th3:
  for i being Integer, n being Nat
  st n = 4*i+3 ex p,q being Nat st p = 4*q+3 & p is prime & p divides n
  proof
    defpred P[Nat] means
    (ex k being Nat st $1=4*k+3) implies
    ex p,q being Nat st p=4*q+3 & p is prime & p divides $1;
    let k be Integer, n be Nat such that
    A1: n = 4*k+3;
    now
      assume k < 0;
      then
B2:   k+1 <= 0 by INT_1:7;
      4*k+3-3 >= 0-3 by A1,XREAL_1:9;
      then 4*k/4 >= (-3)/4 by XREAL_1:72;
      then k+1 >= -3/4+1 by XREAL_1:7;
      hence contradiction by B2,XXREAL_0:2;
    end;
    then reconsider k as Element of NAT by INT_1:3;
B1: n=4*k+3 by A1;
    A2: for m being Nat st for l being Nat st l < m holds P[l] holds P[m]
    proof
      let m be Nat;
      assume A3: for l being Nat st l < m holds P[l];
      given k being Nat such that
      A4: m=4*k+3;
      m <> 0 & m <> 1 by A4,NAT_1:11;
      then m is non trivial by NAT_2:28;
      then consider l being prime Nat such that
      A5: l divides m by NEWTON03:29;
      reconsider l as Element of NAT by ORDINAL1:def 12;
      consider t being Nat such that
      A6: m = l*t by A5,NAT_D:def 3;
      A7: t divides m by A6;
      consider u being Element of NAT such that
      A8: l=4*u or l=4*u+1 or l=4*u+2 or l=4*u+3 by SCHEME1:3;
      per cases by A8;
      suppose l=4*u;
        then 4 divides l;
        then 4 divides m by A5,NAT_D:4;
        hence ex p,q being Nat st
        p=4*q+3 & p is prime & p divides m by A4,NUMBER02:32;
      end;
      suppose A9: l=4*u+1;
        reconsider t as Element of NAT by ORDINAL1:def 12;
        consider v being Element of NAT such that
        A10: t=4*v or t=4*v+1 or t=4*v+2 or t=4*v+3 by SCHEME1:3;
        per cases by A10;
        suppose t=4*v;
          then 4 divides t;
          then 4 divides m by A7,NAT_D:4;
          hence ex p,q being Nat st
          p=4*q+3 & p is prime & p divides m by A4,NUMBER02:32;
        end;
        suppose t=4*v+1;
          then m=4*(4*u*v+u+v)+1 by A6,A9;
          then A11: m mod 4 = 1 mod 4 by NAT_D:21
          .= 1 by NAT_D:24;
          m mod 4 = 3 mod 4 by A4,NAT_D:21
          .= 3 by NAT_D:24;
          hence ex p,q being Nat st
          p=4*q+3 & p is prime & p divides m by A11;
        end;
        suppose t=4*v+2;
          then t=2*(2*v+1);
          then A12: 2 divides t;
          m=2*(2*k+1)+1 by A4;
          hence ex p,q being Nat st
          p=4*q+3 & p is prime & p divides m by A12,A7;
        end;
        suppose A13: t=4*v+3;
          A14: t <= m by A6,NAT_D:def 3,INT_2:27;
          now
            assume t=m;
            then l=1 by A6,A4,XCMPLX_1:7;
            hence contradiction by INT_2:def 4;
          end; then
          t < m by A14,XXREAL_0:1;
          then consider p,q being Nat such that
          A15: p=4*q+3 & p is prime & p divides t by A13,A3;
          take p,q;
          thus p=4*q+3 & p is prime & p divides m by A15,A7,NAT_D:4;
        end;
      end;
      suppose l=4*u+2;
        then l=2*(2*u+1);
        then A16: 2 divides l;
        m=2*(2*k+1)+1 by A4;
        hence ex p,q being Nat st
        p=4*q+3 & p is prime & p divides m by A16,A5;
      end;
      suppose l=4*u+3;
        hence ex p,q being Nat st
        p=4*q+3 & p is prime & p divides m by A5;
      end;
    end;
    for n being Nat holds P[n] from NAT_1:sch 4(A2);
    then consider p,q being Nat such that
    A17: p=4*q+3 & p is prime & p divides n by B1;
    take p,q;
    thus thesis by A17;
  end;

definition
  defpred P[set] means ex k being Nat st $1=4*k+3 & 4*k+3 is prime;
  func 4k+3_Primes -> Subset of NAT means :Def1:
  for n being Nat holds n in it iff ex k being Nat st n=4*k+3 & n is prime;
  existence
  proof
    consider s being Subset of NAT such that
    A1: for x being set holds x in s iff x in NAT & P[x] from SUBSET_1:sch 1;
    take s;
    let n be Nat;
    thus n in s implies ex k being Nat st n=4*k+3 & n is prime
    proof
      assume n in s;
      then consider k being Nat such that
      A2: n=4*k+3 & 4*k+3 is prime by A1;
      thus thesis by A2;
    end;
    given k being Nat such that A3: n=4*k+3 & n is prime;
    thus n in s by A3,A1;
  end;
  uniqueness
  proof
    let s1,s2 be Subset of NAT such that
    A4: for n being Nat holds n in s1 iff
    ex k being Nat st n=4*k+3 & n is prime
    and
    A5: for n being Nat holds n in s2 iff
    ex k being Nat st n=4*k+3 & n is prime;
    A6: for n being Element of NAT holds n in s1 iff P[n]
    proof
      let n be Element of NAT;
      thus n in s1 implies P[n]
      proof
        assume n in s1;
        then consider k being Nat such that
        A7: n=4*k+3 & n is prime by A4;
        thus P[n] by A7;
      end;
      assume P[n];
      then consider k being Nat such that
      A8: n=4*k+3 & 4*k+3 is prime;
      thus n in s1 by A8,A4;
    end;
    A9: for n being Element of NAT holds n in s2 iff P[n]
    proof
      let n be Element of NAT;
      thus n in s2 implies P[n]
      proof
        assume n in s2;
        then consider k being Nat such that
        A10: n=4*k+3 & n is prime by A5;
        thus P[n] by A10;
      end;
      assume P[n];
      then ex k being Nat st n=4*k+3 & 4*k+3 is prime;
      hence n in s2 by A5;
    end;
    thus s1=s2 from SUBSET_1:sch 2(A6,A9);
  end;
end;

theorem Th4:
  for n being Nat st n in 4k+3_Primes holds n >= 3
  proof
    let n be Nat;
    assume n in 4k+3_Primes;
    then consider k being Nat such that
    A1: n=4*k+3 & n is prime by Def1;
    thus n >= 3 by A1,NAT_1:11;
  end;

registration
  cluster 4k+3_Primes -> infinite;
  coherence
  proof
    3=4*0+3 & 3 is prime by PEPIN:41; then
    A1: 3 in 4k+3_Primes by Def1;
    assume 4k+3_Primes is finite;
    then consider n being Element of NAT such that
    A2: 4k+3_Primes c= Seg n \/ {0} by A1,HEYTING3:1;
    A3: 4k+3_Primes c= Seg n by A2,ZFMISC_1:135,Th4;
    set X=4k+3_Primes\{3};
    X c= 4k+3_Primes by XBOOLE_1:36;
    then X c= Seg n by A3,XBOOLE_1:1;
    then a4: X is included_in_Seg by FINSEQ_1:def 13;
    set N=4*(Product Sgm X) + 3;
    consider p,q being Nat such that
    A5: p=4*q+3 & p is prime & p divides N by Th3;
    A6: p in 4k+3_Primes by Def1,A5;
    rng Sgm X c= SetPrimes
    proof
      let a be object;
      assume A7: a in rng Sgm X;
      then a in X by a4,FINSEQ_1:def 14;
      then A8: a in 4k+3_Primes by XBOOLE_0:def 5;
      reconsider n=a as Nat by A7;
      consider k being Nat such that
      A9: n=4*k+3 & n is prime by A8,Def1;
      thus a in SetPrimes by A9,NEWTON:def 6;
    end;
    then reconsider SX=Sgm X as FinSequence of SetPrimes by FINSEQ_1:def 4;
    for p being prime Nat st p in 4k+3_Primes holds not p divides N
    proof
      let p be prime Nat;
      assume A10: p in 4k+3_Primes;
      assume A11: p divides N;
      p >= 3 by A10,Th4;
      then per cases by XXREAL_0:1;
      suppose A12: p=3;
        2,3 are_coprime by INT_2:30,INT_2:28,PEPIN:41;
        then A13: 2*2,3 are_coprime by EULER_1:14;
        p divides 4*(Product Sgm X) by A11,A12,INT_2:1;
        then p in rng SX by A12,A13,EULER_1:13,NAT_3:8;
        then p in X by a4,FINSEQ_1:def 14;
        then not p in {3} by XBOOLE_0:def 5;
        hence contradiction by A12,TARSKI:def 1;
      end;
      suppose A14: p>3;
        then not p in {3} by TARSKI:def 1;
        then p in X by A10,XBOOLE_0:def 5;
        then p in rng SX by a4,FINSEQ_1:def 14;
        then p divides 4*Product Sgm X by NAT_D:9,NAT_3:7;
        hence contradiction by A14,INT_2:1,27,A11;
      end;
      end;
    hence contradiction by A5,A6;
  end;
end;

:: Problem 13
theorem
  for n being Nat st n in 4k+3_Primes
  for x being even Nat
  for i being Nat holds not n divides x|^|^(i+2) + 1
  proof
    let n be Nat;
    assume A1: n in 4k+3_Primes;
    then A2: n >= 3 by Th4;
    let x be even Nat;
    let i be Nat;
    reconsider i2=i+2 as Nat;
    consider m being Element of NAT such that
    A3: i2 = 2*m or i2 = 2*m+1 by SCHEME1:1;
    per cases;
    suppose A4: x is zero;
      per cases by A3;
      suppose i+2=2*m;
        then A5: x|^|^(i+2) = 1 by A4,ORDINAL5:20;
        assume n divides x|^|^(i+2) + 1;
        then n <= 2 by INT_2:27,A5;
        hence contradiction by A2,XXREAL_0:2;
      end;
      suppose i+2=2*m+1;
        then A6: x|^|^(i+2) = 0 by A4,ORDINAL5:20;
        assume n divides x|^|^(i+2) + 1;
        then n <= 1 by INT_2:27,A6;
        hence contradiction by A2,XXREAL_0:2;
      end;
    end;
    suppose x is non zero;
      then consider m being Nat such that
      A7: x|^|^(i+1) = 2*m by ABIAN:def 2;
      A8: x|^|^((i+1)+1) = x|^|^(Segm((i+1)+1))
      .= x|^|^(succ Segm(i+1)) by NAT_1:38
      .= exp(x,x|^|^(i+1)) by ORDINAL5:14
      .= x|^(m*2) by A7
      .= (x|^m)|^2 by NEWTON:9;
      assume n divides x|^|^(i+2) + 1;
      then (x|^m)|^2 -  -1 mod n = 0 by A8;
      then A9: (x|^m)^2 -  -1 mod n = 0 by WSIERP_1:1;
      consider k being Nat such that
      A10: n=4*k+3 & n is prime by A1,Def1;
      A11: n mod 4 = 3 mod 4 by A10,NAT_D:21
      .= 3 by NAT_D:24;
      n > 2 by A2,XXREAL_0:2;
      hence contradiction by A11,A9,INT_5:def 2,A10,INT_5:38;
    end;
  end;

begin :: Problem 31

theorem Th6:
  for a being Integer st not 3 divides a holds a|^3 mod 9 = 1 or a|^3 mod 9 = 8
  proof
    let a be Integer;
    assume not 3 divides a;
    then a mod 3 <> 0 by INT_1:62;
    then a mod 3 > 0 & a mod 3 < 3 by INT_1:58;
    then A1: a mod 3 > 0 & a mod 3 in Segm 3 by NAT_1:44;
    set d = a div 3;
    A2:
    now
      assume a mod 3 = 1;
      then a = d*3 + 1 by INT_1:59;
      then a|^3 = (3*d)|^3+3*(3*d)|^2+3*(3*d)+1 by SERIES_2:2
      .= (3|^3*d|^3)+3*(3*d)|^2+3*(3*d)+1 by NEWTON:7
      .= ((3*3*3)*d|^3)+3*(3*d)|^2+3*(3*d)+1 by POLYEQ_3:27
      .= ((3*3*3)*d|^3)+3*((3|^2*d|^2))+3*(3*d)+1 by NEWTON:7
      .= ((3*3*3)*d|^3)+3*((3*3)*d|^2)+3*(3*d)+1 by WSIERP_1:1
      .= 9*(3*d|^3+3*d|^2+d)+1;
      hence a|^3 mod 9 = ((9*(3*d|^3+3*d|^2+d) mod 9) + (1 mod 9)) mod 9
      by NAT_D:66
      .= (0 + (1 mod 9)) mod 9
      .= 1 by NAT_D:63;
    end;
    A3:
    now
      assume a mod 3 = 2;
      then a = d*3 + 2 by INT_1:59;
      then a|^3 = (3*d)|^3+3*(3*d)|^2*2+3*2|^2*(3*d)+2|^3 by SERIES_4:2
      .= (3|^3*d|^3)+3*(3*d)|^2*2+3*2|^2*(3*d)+2|^3 by NEWTON:7
      .= ((3*3*3)*d|^3)+3*(3*d)|^2*2+3*2|^2*(3*d)+2|^3 by POLYEQ_3:27
      .= ((3*3*3)*d|^3)+3*(3|^2*d|^2)*2+3*2|^2*(3*d)+2|^3 by NEWTON:7
      .= ((3*3*3)*d|^3)+3*((3*3)*d|^2)*2+3*2|^2*(3*d)+2|^3 by WSIERP_1:1
      .= 9*(3*d|^3+3*d|^2*2+2|^2*d)+(2*2*2) by POLYEQ_3:27;
      hence a|^3 mod 9 = ((9*(3*d|^3+3*d|^2*2+2|^2*d)) mod 9 +
      ((2*2*2) mod 9)) mod 9 by NAT_D:66
      .= (0 + (8 mod 9)) mod 9
      .= 8 by NAT_D:63;
    end;
    thus thesis by A2,A3,A1,ENUMSET1:def 1,CARD_1:51;
  end;

:: Problem 31
theorem
  for a,b,c being Integer st 9 divides a|^3+b|^3+c|^3 holds
  3 divides a or 3 divides b or 3 divides c
  proof
    let a,b,c be Integer;
    assume 9 divides a|^3+b|^3+c|^3;
    then A1: a|^3+b|^3+c|^3 mod 9 = 0;
    assume not 3 divides a & not 3 divides b & not 3 divides c;
    then per cases by Th6;
    suppose A2: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
       .= (2 + 1) mod 9 by A2,NAT_D:63;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A3: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (2+8) mod 9 by A3,NAT_D:63
      .= (1+9) mod 9
      .= ((1 mod 9) + (9 mod 9)) mod 9 by NAT_D:66
      .= ((1 mod 9) + 0) mod 9 by INT_1:50;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A4: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (0+1) mod 9 by A4,INT_1:50;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A5: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (0+8) mod 9 by A5,INT_1:50;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A6: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (0+1) mod 9 by A6,INT_1:50;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A7: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (0+8) mod 9 by A7,INT_1:50;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A8: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (((9 + 7) mod 9) + 1) mod 9 by A8
      .= ((((9 mod 9) + (7 mod 9)) mod 9) + 1) mod 9 by NAT_D:66
      .= (((0 + (7 mod 9)) mod 9) + 1) mod 9 by INT_1:50
      .= (7+1) mod 9 by NAT_D:63;
      hence contradiction by A1,NAT_D:63;
    end;
    suppose A9: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3) mod 9 = (((a|^3+b|^3) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= ((((a|^3 mod 9) + (b|^3 mod 9)) mod 9) + (c|^3 mod 9)) mod 9
      by NAT_D:66
      .= (((9 + 7) mod 9) + 8) mod 9 by A9
      .= ((((9 mod 9) + (7 mod 9)) mod 9) + 8) mod 9 by NAT_D:66
      .= (((0 + (7 mod 9)) mod 9) + 8) mod 9 by INT_1:50
      .= (7+8) mod 9 by NAT_D:63
      .= (6+9) mod 9
      .= ((6 mod 9) + (9 mod 9)) mod 9 by NAT_D:66
      .= ((6 mod 9) + 0) mod 9 by INT_1:50
      .= 6 mod 9;
      hence contradiction by A1,NAT_D:63;
    end;
  end;

begin :: Problem 32

theorem Th8:
  for a,b,c,n being Integer holds
  (a+b+c) mod n = ((a mod n)+(b mod n)+(c mod n)) mod n
  proof
    let a,b,c,n be Integer;
    thus (a+b+c) mod n = ((a+b) mod n + (c mod n)) mod n by NAT_D:66
    .= ((((a mod n) + (b mod n)) mod n) + ((c mod n) mod n)) mod n by NAT_D:66
    .= ((a mod n)+(b mod n)+(c mod n)) mod n by NAT_D:66;
  end;

theorem Th9:
  for a,b,c,d,n being Integer holds
  (a+b+c+d) mod n = ((a mod n)+(b mod n)+(c mod n)+(d mod n)) mod n
  proof
    let a,b,c,d,n be Integer;
    thus (a+b+c+d) mod n = ((a+b+c) mod n + (d mod n)) mod n by NAT_D:66
    .= ((((a mod n)+(b mod n)+(c mod n)) mod n) +((d mod n) mod n)) mod n
    by Th8
    .= ((a mod n)+(b mod n)+(c mod n)+(d mod n)) mod n by NAT_D:66;
  end;

theorem Th10:
  for a,b,c,d,e,n being Integer holds
  (a+b+c+d+e) mod n = ((a mod n)+(b mod n)+(c mod n)+(d mod n)+(e mod n)) mod n
  proof
    let a,b,c,d,e,n being Integer;
    thus (a+b+c+d+e) mod n = ((a+b+c+d) mod n + (e mod n)) mod n by NAT_D:66
    .= ((((a mod n)+(b mod n)+(c mod n)+(d mod n)) mod n) + ((e mod n) mod n))
    mod n by Th9
    .= ((a mod n)+(b mod n)+(c mod n)+(d mod n)+(e mod n)) mod n by NAT_D:66;
  end;

:: Problem 32
theorem
  for a1,a2,a3,a4,a5 being Integer st 9 divides a1|^3+a2|^3+a3|^3+a4|^3+a5|^3
  holds 3 divides a1*a2*a3*a4*a5
  proof
    let a,b,c,d,e be Integer;
    assume 9 divides a|^3+b|^3+c|^3+d|^3+e|^3;
    then A1: a|^3+b|^3+c|^3+d|^3+e|^3 mod 9 = 0;
    assume A2: not 3 divides a*b*c*d*e;
    then A3: not 3 divides a*(b*c*d*e);
    A4: not 3 divides b*(a*c*d*e) by A2;
    A5: not 3 divides c*(a*b*d*e) by A2;
    not 3 divides d*(a*b*c*e) by A2;
    then per cases by Th6,A3,A4,A5,A2,INT_2:2;

    suppose A6: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+1+1+1) mod 9 by A6,Th10;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A7: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+1+1+8) mod 9 by A7,Th10
      .= (9*1 + 3) mod 9
      .= ((9*1) mod 9 + (3 mod 9)) mod 9 by NAT_D:66
      .= ((9*1) mod 9 + 3) mod 9
      .= (0 + 3) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A8: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+1+8+1) mod 9 by A8,Th10
      .= (9*1 + 3) mod 9
      .= ((9*1) mod 9 + (3 mod 9)) mod 9 by NAT_D:66
      .= ((9*1) mod 9 + 3) mod 9
      .= (0 + 3) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A9: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+1+8+8) mod 9 by A9,Th10
      .= (9*2 + 1) mod 9
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A10: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+8+1+1) mod 9 by A10,Th10
      .= (9*1 + 3) mod 9
      .= ((9*1) mod 9 + (3 mod 9)) mod 9 by NAT_D:66
      .= ((9*1) mod 9 + 3) mod 9
      .= (0 + 3) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A11: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+8+1+8) mod 9 by A11,Th10
      .= (9*2 + 1) mod 9
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A12: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+8+8+1) mod 9 by A12,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A13: a|^3 mod 9 = 1 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+1+8+8+8) mod 9 by A13,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A14: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+1+1+1) mod 9 by A14,Th10
      .= (9*1 + 3) mod 9
      .= ((9*1) mod 9 + (3 mod 9)) mod 9 by NAT_D:66
      .= ((9*1) mod 9 + 3) mod 9
      .= (0 + 3) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A15: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+1+1+8) mod 9 by A15,Th10
      .= (9*2 + 1) mod 9
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A16: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+1+8+1) mod 9 by A16,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A17: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+1+8+8) mod 9 by A17,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A18: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+8+1+1) mod 9 by A18,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A19: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+8+1+8) mod 9 by A19,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A20: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+8+8+1) mod 9 by A20,Th10
      .= (9*2 + 8) mod 9
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A21: a|^3 mod 9 = 1 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (1+8+8+8+8) mod 9 by A21,Th10
      .= (9*3 + 6) mod 9
      .= ((9*3) mod 9 + (6 mod 9)) mod 9 by NAT_D:66
      .= ((9*3) mod 9 + 6) mod 9
      .= (0 + 6) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A22: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+1+1+1) mod 9 by A22,Th10
      .= (9*1 + 3) mod 9
      .= ((9*1) mod 9 + (3 mod 9)) mod 9 by NAT_D:66
      .= ((9*1) mod 9 + 3) mod 9
      .= (0 + 3) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A23: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+1+1+8) mod 9 by A23,Th10
      .= (9*2 + 1) mod 9
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A24: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+1+8+1) mod 9 by A24,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A25: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+1+8+8) mod 9 by A25,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A26: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+8+1+1) mod 9 by A26,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A27: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+8+1+8) mod 9 by A27,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A28: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+8+8+1) mod 9 by A28,Th10
      .= (9*2 + 8) mod 9
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A29: a|^3 mod 9 = 8 & b|^3 mod 9 = 1 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+1+8+8+8) mod 9 by A29,Th10
      .= (9*3 + 6) mod 9
      .= ((9*3) mod 9 + (6 mod 9)) mod 9 by NAT_D:66
      .= ((9*3) mod 9 + 6) mod 9
      .= (0 + 6) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A30: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+1+1+1) mod 9 by A30,Th10
      .= ((9*2) mod 9 + (1 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 1) mod 9
      .= (0 + 1) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A31: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+1+1+8) mod 9 by A31,Th10
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A32: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+1+8+1) mod 9 by A32,Th10
      .= (9*2 + 8) mod 9
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A33: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 1
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+1+8+8) mod 9 by A33,Th10
      .= (9*3 + 6) mod 9
      .= ((9*3) mod 9 + (6 mod 9)) mod 9 by NAT_D:66
      .= ((9*3) mod 9 + 6) mod 9
      .= (0 + 6) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A34: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+8+1+1) mod 9 by A34,Th10
      .= (9*2 + 8) mod 9
      .= ((9*2) mod 9 + (8 mod 9)) mod 9 by NAT_D:66
      .= ((9*2) mod 9 + 8) mod 9
      .= (0 + 8) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A35: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 1 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+8+1+8) mod 9 by A35,Th10
      .= (9*3 + 6) mod 9
      .= ((9*3) mod 9 + (6 mod 9)) mod 9 by NAT_D:66
      .= ((9*3) mod 9 + 6) mod 9
      .= (0 + 6) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A36: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 1;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+8+8+1) mod 9 by A36,Th10
      .= (9*3 + 6) mod 9
      .= ((9*3) mod 9 + (6 mod 9)) mod 9 by NAT_D:66
      .= ((9*3) mod 9 + 6) mod 9
      .= (0 + 6) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;

    suppose A37: a|^3 mod 9 = 8 & b|^3 mod 9 = 8 & c|^3 mod 9 = 8
      & d|^3 mod 9 = 8 & e|^3 mod 9 = 8;
      ((a|^3+b|^3)+c|^3+d|^3+e|^3) mod 9 = (8+8+8+8+8) mod 9 by A37,Th10
      .= (9*4 + 4) mod 9
      .= ((9*4) mod 9 + (4 mod 9)) mod 9 by NAT_D:66
      .= ((9*4) mod 9 + 4) mod 9
      .= (0 + 4) mod 9;
      hence contradiction by A1,NAT_D:63;
    end;
  end;

begin :: Problem 33

reserve a,b,c,k,m,n for Nat;
reserve p for Prime;

::$CT

Lm1:
  for x,y,z being Nat st
  x,y are_coprime & x|^2+y|^2 = z|^4 & x is odd holds 7 divides x*y
  proof
    let x,y,z be Nat such that
A1: x,y are_coprime and
A2: x|^2+y|^2 = z|^4;
    per cases;
    suppose 7 divides y;
      hence thesis by INT_2:2;
    end;
    suppose
A3:   not 7 divides y;
      set c = z|^2;
A4:   x|^2 = x^2 & y|^2 = y^2 by NEWTON:81;
A5:   z|^2 = z^2 by NEWTON:81;
A6:   z|^(2+2) = c^2 by NEWTON:8;
      assume x is odd;
      then consider n,m being Element of NAT such that
      n <= m and
A7:   x = m^2 - n^2 and
A8:   y = 2*n*m and
A9:   z^2 = m^2 + n^2 by A1,A2,A4,A5,A6,PYTHTRIP:11;
A10:  not 7 divides m by A3,A8,INT_2:2;
      y = n*(2*m) by A8;
      then
A11:  not 7 divides n by A3,INT_2:2;
A12:  z^2 mod 7 = 0 or z^2 mod 7 = 1 or z^2 mod 7 = 2 or z^2 mod 7 = 4
      by NUMBER02:49;
A13:  m^2 mod 7 = ((m mod 7) * (m mod 7)) mod 7 &
      n^2 mod 7 = ((n mod 7) * (n mod 7)) mod 7 by NAT_D:67;
A14:  (m^2+n^2) mod 7 = ((m^2 mod 7) + (n^2 mod 7)) mod 7 by NAT_D:66;
A15:  (1*7+2) mod 7 = 2 & (2*7+2) mod 7 = 2 & (3*7+4) mod 7 = 4 &
      (5*7+1) mod 7 = 1 by NUMBER02:16;
      (m mod (6+1) = 0 or ... or m mod (6+1) = 6) &
      (n mod (6+1) = 0 or ... or n mod (6+1) = 6) by NUMBER03:11;
      then ((m^2 mod 7) - (n^2 mod 7)) mod 7 = 0
      by A9,A10,A11,A12,A13,A14,A15,NAT_D:24,INT_1:62;
      then (m^2 - n^2) mod 7 = 0 by INT_6:7;
      then 7 divides x by A7,INT_1:62;
      hence thesis by INT_2:2;
    end;
  end;

:: Problem 33 a
theorem
  for x,y,z being Nat st x,y are_coprime & x|^2+y|^2 = z|^4 holds 7 divides x*y
  proof
    let x,y,z be Nat;
    assume
A1: x,y are_coprime;
    then x is odd or y is odd by NEWTON05:35;
    hence thesis by A1,Lm1;
  end;

:: Problem 33 b
theorem
  not 15,20 are_coprime & 15|^2+20|^2 = 5|^4 & not 7 divides 15*20
  proof
    (3*1+1) mod 3 = 1 by NUMBER02:16;
    then
A1: 1 = 3 gcd (4 mod 3) by NEWTON:51
    .= 4 gcd 3 by NAT_D:30;
    (5*3) gcd (5*4) = 5*(3 gcd 4) by PYTHTRIP:8;
    hence not 15,20 are_coprime by A1;
A2: 15|^2 = 15*15 & 20|^2 = 20*20 by WSIERP_1:1;
    5|^4 = 5*5*5*5 by POLYEQ_5:3;
    hence 15|^2+20|^2 = 5|^4 by A2;
    15*20 = 7*42+6;
    then 15*20 mod 7 = 6 by NUMBER02:16;
    hence not 7 divides 15*20;
  end;

begin :: Problem 35

definition
  let x,y be Nat;
  pred x,y satisfy_Sierpinski_problem_35 means
  x*(x+1) divides y*(y+1) & not x divides y & not x+1 divides y &
  not x divides y+1 & not x+1 divides y+1;
end;

theorem Th15:
  for x,y being Nat st x = 36*k+14 & y = (12*k+5)*(18*k+7) holds
  x,y satisfy_Sierpinski_problem_35
  proof
    let x,y be Nat such that
A1: x = 36*k+14 and
A2: y = (12*k+5)*(18*k+7);
A3: x*(x+1) = 2*3*(12*k+5)*(18*k+7) = 6*y by A1,A2;
    y+1 = 6*(36*k*k+29*k+6) by A2;
    then 6 divides y+1;
    hence x*(x+1) divides y*(y+1) by A2,A3,INT_4:7;
A4: x = 2*(18*k+7) by A1;
    y = 2*(108*k*k+87*k+17)+1 by A2;
    hence not x divides y by A4;
A5: x+1 = 3*(12*k+5) by A1;
    then
A6: 3 divides x+1;
    y = 3*(72*k*k+58*k+11)+2 by A2;
    hence not x+1 divides y by A6,INT_2:9,NAT_4:9;
    0+7 <= 18*k+7 by XREAL_1:6;
    then
A7: 18*k+7 <> 1;
A8: 18*k+7 divides x by A4;
    18*k+7 divides y by A2;
    then not 18*k+7 divides y+1 by A7,NEWTON:39;
    hence not x divides y+1 by A8,INT_2:9;
    0+5 <= 12*k+5 by XREAL_1:6;
    then
A9: 12*k+5 <> 1;
A10: 12*k+5 divides x+1 by A5;
    12*k+5 divides y by A2;
    then not 12*k+5 divides y+1 by A9,NEWTON:39;
    hence not x+1 divides y+1 by A10,INT_2:9;
  end;

:: Problem 35 a
theorem
  {[x,y] where x,y is Nat: x,y satisfy_Sierpinski_problem_35} is infinite
  proof
    set A = {[x,y] where x,y is Nat: x,y satisfy_Sierpinski_problem_35};
    deffunc F(Nat) = [36*$1+14,(12*$1+5)*(18*$1+7)];
    consider f being ManySortedSet of NAT such that
A1: for d being Element of NAT holds f.d = F(d) from PBOOLE:sch 5;
A2: dom f = NAT by PARTFUN1:def 2;
A3: rng f c= A
    proof
      let y be object;
      assume y in rng f;
      then consider k being object such that
A4:   k in dom f and
A5:   f.k = y by FUNCT_1:def 3;
      reconsider k as Element of NAT by A4,PARTFUN1:def 2;
      36*k+14,(12*k+5)*(18*k+7) satisfy_Sierpinski_problem_35 by Th15;
      then F(k) in A;
      hence thesis by A1,A5;
    end;
    f is one-to-one
    proof
      let x1,x2 be object such that
A6:   x1 in dom f & x2 in dom f and
A7:   f.x1 = f.x2;
      reconsider x1,x2 as Element of NAT by A6,PARTFUN1:def 2;
      f.x1 = F(x1) & f.x2 = F(x2) by A1;
      then 36*x1+14 = 36*x2+14 by A7,XTUPLE_0:1;
      hence thesis;
    end;
    hence thesis by A2,A3,CARD_1:59;
  end;

:: Problem 35 b
theorem
  14,35 satisfy_Sierpinski_problem_35
  proof
    1260 = 6*210;
    hence 14*(14+1) divides 35*(35+1);
    35 = 2*14+7;
    hence not 14 divides 35 by NAT_4:9;
    35 = 2*15+5;
    hence not 14+1 divides 35 by NAT_4:9;
    36 = 2*14+8;
    hence not 14 divides 35+1 by NAT_4:9;
    36 = 2*15+6;
    hence not 14+1 divides 35+1 by NAT_4:9;
  end;

:: Problem 35 c
theorem
  not ex x,y being Nat st x < 14 & y < 35 & x,y satisfy_Sierpinski_problem_35
  proof
    given x,y being Nat such that
A1: x < 14 and
A2: y < 35 and
A3: x,y satisfy_Sierpinski_problem_35;
    14 = 13+1;
    then x <= 13 by A1,NAT_1:13;
    then
A4: x = 0 or ... or x = 13;
    35 = 34+1;
    then y <= 34 by A2,NAT_1:13;
    then
A5: y = 0 or ... or y = 34;
    per cases by A4;
    suppose x = 0;
      hence contradiction by A3,NAT_D:6;
    end;
    suppose x = 1;
      hence contradiction by A3,NAT_D:6;
    end;
    suppose
A6:   x = 2;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A6;
      end;
      suppose y = 2;
        hence contradiction by A3,A6;
      end;
      suppose y = 3;
        hence contradiction by A3,A6;
      end;
      suppose
A7:     y = 4;
        2 divides 2*2;
        hence contradiction by A3,A6,A7;
      end;
      suppose
A8:     y = 5;
        2 divides 2*3;
        hence contradiction by A3,A6,A8;
      end;
      suppose
A9:     y = 6;
        2 divides 2*3;
        hence contradiction by A3,A6,A9;
      end;
      suppose
A10:    y = 7;
        2 divides 2*4;
        hence contradiction by A3,A6,A10;
      end;
      suppose
A11:    y = 8;
        2 divides 2*4;
        hence contradiction by A3,A6,A11;
      end;
      suppose
A12:    y = 9;
        2 divides 2*5;
        hence contradiction by A3,A6,A12;
      end;
      suppose
A13:    y = 10;
        2 divides 2*5;
        hence contradiction by A3,A6,A13;
      end;
      suppose
A14:    y = 11;
        2 divides 2*6;
        hence contradiction by A3,A6,A14;
      end;
      suppose
A15:    y = 12;
        2 divides 2*6;
        hence contradiction by A3,A6,A15;
      end;
      suppose
A16:    y = 13;
        2 divides 2*7;
        hence contradiction by A3,A6,A16;
      end;
      suppose
A17:    y = 14;
        2 divides 2*7;
        hence contradiction by A3,A6,A17;
      end;
      suppose
A18:    y = 15;
        2 divides 2*8;
        hence contradiction by A3,A6,A18;
      end;
      suppose
A19:    y = 16;
        2 divides 2*8;
        hence contradiction by A3,A6,A19;
      end;
      suppose
A20:    y = 17;
        2 divides 2*9;
        hence contradiction by A3,A6,A20;
      end;
      suppose
A21:    y = 18;
        2 divides 2*9;
        hence contradiction by A3,A6,A21;
      end;
      suppose
A22:    y = 19;
        2 divides 2*10;
        hence contradiction by A3,A6,A22;
      end;
      suppose
A23:    y = 20;
        2 divides 2*10;
        hence contradiction by A3,A6,A23;
      end;
      suppose
A24:    y = 21;
        2 divides 2*11;
        hence contradiction by A3,A6,A24;
      end;
      suppose
A25:    y = 22;
        2 divides 2*11;
        hence contradiction by A3,A6,A25;
      end;
      suppose
A26:    y = 23;
        2 divides 2*12;
        hence contradiction by A3,A6,A26;
      end;
      suppose
A27:    y = 24;
        2 divides 2*12;
        hence contradiction by A3,A6,A27;
      end;
      suppose
A28:    y = 25;
        2 divides 2*13;
        hence contradiction by A3,A6,A28;
      end;
      suppose
A29:    y = 26;
        2 divides 2*13;
        hence contradiction by A3,A6,A29;
      end;
      suppose
A30:    y = 27;
        2 divides 2*14;
        hence contradiction by A3,A6,A30;
      end;
      suppose
A31:    y = 28;
        2 divides 2*14;
        hence contradiction by A3,A6,A31;
      end;
      suppose
A32:    y = 29;
        2 divides 2*15;
        hence contradiction by A3,A6,A32;
      end;
      suppose
A33:    y = 30;
        2 divides 2*15;
        hence contradiction by A3,A6,A33;
      end;
      suppose
A34:    y = 31;
        2 divides 2*16;
        hence contradiction by A3,A6,A34;
      end;
      suppose
A35:    y = 32;
        2 divides 2*16;
        hence contradiction by A3,A6,A35;
      end;
      suppose
A36:    y = 33;
        2 divides 2*17;
        hence contradiction by A3,A6,A36;
      end;
      suppose
A37:    y = 34;
        2 divides 2*17;
        hence contradiction by A3,A6,A37;
      end;
    end;
    suppose
A38:  x = 3;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A38,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A38;
      end;
      suppose y = 3;
        hence contradiction by A3,A38;
      end;
      suppose y = 4;
        hence contradiction by A3,A38;
      end;
      suppose
A39:    y = 5;
        3 divides 3*2;
        hence contradiction by A3,A38,A39;
      end;
      suppose
A40:    y = 6;
        3 divides 3*2;
        hence contradiction by A3,A38,A40;
      end;
      suppose
A41:    y = 7;
        4 divides 4*2;
        hence contradiction by A3,A38,A41;
      end;
      suppose
A42:    y = 8;
        4 divides 4*2;
        hence contradiction by A3,A38,A42;
      end;
      suppose
A43:    y = 9;
        3 divides 3*3;
        hence contradiction by A3,A38,A43;
      end;
      suppose
A44:    y = 10;
        110 = 12*9+2;
        hence contradiction by A3,A38,A44,NAT_4:9;
      end;
      suppose
A45:    y = 11;
        3 divides 3*4;
        hence contradiction by A3,A38,A45;
      end;
      suppose
A46:    y = 12;
        3 divides 3*4;
        hence contradiction by A3,A38,A46;
      end;
      suppose
A47:    y = 13;
        182 = 12*15+2;
        hence contradiction by A3,A38,A47,NAT_4:9;
      end;
      suppose
A48:    y = 14;
        3 divides 3*5;
        hence contradiction by A3,A38,A48;
      end;
      suppose
A49:    y = 15;
        3 divides 3*5;
        hence contradiction by A3,A38,A49;
      end;
      suppose
A50:    y = 16;
        4 divides 4*4;
        hence contradiction by A3,A38,A50;
      end;
      suppose
A51:    y = 17;
        3 divides 3*6;
        hence contradiction by A3,A38,A51;
      end;
      suppose
A52:    y = 18;
        3 divides 3*6;
        hence contradiction by A3,A38,A52;
      end;
      suppose
A53:    y = 19;
        380 = 12*31+8;
        hence contradiction by A3,A38,A53,NAT_4:9;
      end;
      suppose
A54:    y = 20;
        4 divides 4*5;
        hence contradiction by A3,A38,A54;
      end;
      suppose
A55:    y = 21;
        3 divides 3*7;
        hence contradiction by A3,A38,A55;
      end;
      suppose
A56:    y = 22;
        506 = 12*42+2;
        hence contradiction by A3,A38,A56,NAT_4:9;
      end;
      suppose
A57:    y = 23;
        3 divides 3*8;
        hence contradiction by A3,A38,A57;
      end;
      suppose
A58:    y = 24;
        3 divides 3*8;
        hence contradiction by A3,A38,A58;
      end;
      suppose
A59:    y = 25;
        650 = 12*54+2;
        hence contradiction by A3,A38,A59,NAT_4:9;
      end;
      suppose
A60:    y = 26;
        3 divides 3*9;
        hence contradiction by A3,A38,A60;
      end;
      suppose
A61:    y = 27;
        3 divides 3*9;
        hence contradiction by A3,A38,A61;
      end;
      suppose
A62:    y = 28;
        4 divides 4*7;
        hence contradiction by A3,A38,A62;
      end;
      suppose
A63:    y = 29;
        870 = 12*72+6;
        hence contradiction by A3,A38,A63,NAT_4:9;
      end;
      suppose
A64:    y = 30;
        3 divides 3*10;
        hence contradiction by A3,A38,A64;
      end;
      suppose
A65:    y = 31;
        992 = 12*82+8;
        hence contradiction by A3,A38,A65,NAT_4:9;
      end;
      suppose
A66:    y = 32;
        4 divides 4*8;
        hence contradiction by A3,A38,A66;
      end;
      suppose
A67:    y = 33;
        3 divides 3*11;
        hence contradiction by A3,A38,A67;
      end;
      suppose
A68:    y = 34;
        1190 = 12*99+2;
        hence contradiction by A3,A38,A68,NAT_4:9;
      end;
    end;
    suppose
A69:  x = 4;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A69,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A69,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A69;
      end;
      suppose y = 4;
        hence contradiction by A3,A69;
      end;
      suppose y = 5;
        hence contradiction by A3,A69;
      end;
      suppose
A70:    y = 6;
        42 = 20*2+2;
        hence contradiction by A3,A69,A70,NAT_4:9;
      end;
      suppose
A71:    y = 7;
        56 = 20*2+16;
        hence contradiction by A3,A69,A71,NAT_4:9;
      end;
      suppose
A72:    y = 8;
        4 divides 4*2;
        hence contradiction by A3,A69,A72;
      end;
      suppose
A73:    y = 9;
        90 = 20*4+10;
        hence contradiction by A3,A69,A73,NAT_4:9;
      end;
      suppose
A74:    y = 10;
        110 = 20*5+10;
        hence contradiction by A3,A69,A74,NAT_4:9;
      end;
      suppose
A75:    y = 11;
        132 = 20*6+12;
        hence contradiction by A3,A69,A75,NAT_4:9;
      end;
      suppose
A76:    y = 12;
        4 divides 4*3;
        hence contradiction by A3,A69,A76;
      end;
      suppose
A77:    y = 13;
        182 = 20*9+2;
        hence contradiction by A3,A69,A77,NAT_4:9;
      end;
      suppose
A78:    y = 14;
        210 = 20*10+10;
        hence contradiction by A3,A69,A78,NAT_4:9;
      end;
      suppose
A79:    y = 15;
        4 divides 4*4;
        hence contradiction by A3,A69,A79;
      end;
      suppose
A80:    y = 16;
        4 divides 4*4;
        hence contradiction by A3,A69,A80;
      end;
      suppose
A81:    y = 17;
        306 = 20*15+6;
        hence contradiction by A3,A69,A81,NAT_4:9;
      end;
      suppose
A82:    y = 18;
        342 = 20*17+2;
        hence contradiction by A3,A69,A82,NAT_4:9;
      end;
      suppose
A83:    y = 19;
        4 divides 4*5;
        hence contradiction by A3,A69,A83;
      end;
      suppose
A84:    y = 20;
        4 divides 4*5;
        hence contradiction by A3,A69,A84;
      end;
      suppose
A85:    y = 21;
        462 = 20*23+2;
        hence contradiction by A3,A69,A85,NAT_4:9;
      end;
      suppose
A86:    y = 22;
        506 = 20*25+6;
        hence contradiction by A3,A69,A86,NAT_4:9;
      end;
      suppose
A87:    y = 23;
        4 divides 4*6;
        hence contradiction by A3,A69,A87;
      end;
      suppose
A88:    y = 24;
        4 divides 4*6;
        hence contradiction by A3,A69,A88;
      end;
      suppose
A89:    y = 25;
        650 = 20*32+10;
        hence contradiction by A3,A69,A89,NAT_4:9;
      end;
      suppose
A90:    y = 26;
        702 = 20*35+2;
        hence contradiction by A3,A69,A90,NAT_4:9;
      end;
      suppose
A91:    y = 27;
        4 divides 4*7;
        hence contradiction by A3,A69,A91;
      end;
      suppose
A92:    y = 28;
        4 divides 4*7;
        hence contradiction by A3,A69,A92;
      end;
      suppose
A93:    y = 29;
        870 = 20*43+10;
        hence contradiction by A3,A69,A93,NAT_4:9;
      end;
      suppose
A94:    y = 30;
        930 = 20*46+10;
        hence contradiction by A3,A69,A94,NAT_4:9;
      end;
      suppose
A95:    y = 31;
        4 divides 4*8;
        hence contradiction by A3,A69,A95;
      end;
      suppose
A96:    y = 32;
        4 divides 4*8;
        hence contradiction by A3,A69,A96;
      end;
      suppose
A97:    y = 33;
        1122 = 20*56+2;
        hence contradiction by A3,A69,A97,NAT_4:9;
      end;
      suppose
A98:    y = 34;
        1190 = 20*59+10;
        hence contradiction by A3,A69,A98,NAT_4:9;
      end;
    end;
    suppose
A99:  x = 5;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A99,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A99,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A99,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A99;
      end;
      suppose y = 5;
        hence contradiction by A3,A99;
      end;
      suppose y = 6;
        hence contradiction by A3,A99;
      end;
      suppose
A100:    y = 7;
        56 = 30*1+26;
        hence contradiction by A3,A99,A100,NAT_4:9;
      end;
      suppose
A101:    y = 8;
        72 = 30*2+12;
        hence contradiction by A3,A99,A101,NAT_4:9;
      end;
      suppose
A102:    y = 9;
        5 divides 5*2;
        hence contradiction by A3,A99,A102;
      end;
      suppose
A103:    y = 10;
        5 divides 5*2;
        hence contradiction by A3,A99,A103;
      end;
      suppose
A104:    y = 11;
        132 = 30*4+12;
        hence contradiction by A3,A99,A104,NAT_4:9;
      end;
      suppose
A105:    y = 12;
        6 divides 6*2;
        hence contradiction by A3,A99,A105;
      end;
      suppose
A106:    y = 13;
        182 = 30*6+2;
        hence contradiction by A3,A99,A106,NAT_4:9;
      end;
      suppose
A107:    y = 14;
        5 divides 5*3;
        hence contradiction by A3,A99,A107;
      end;
      suppose
A108:    y = 15;
        5 divides 5*3;
        hence contradiction by A3,A99,A108;
      end;
      suppose
A109:    y = 16;
        272 = 30*9+2;
        hence contradiction by A3,A99,A109,NAT_4:9;
      end;
      suppose
A110:    y = 17;
        306 = 30*10+6;
        hence contradiction by A3,A99,A110,NAT_4:9;
      end;
      suppose
A111:    y = 18;
        6 divides 6*3;
        hence contradiction by A3,A99,A111;
      end;
      suppose
A112:    y = 19;
        5 divides 5*4;
        hence contradiction by A3,A99,A112;
      end;
      suppose
A113:    y = 20;
        5 divides 5*4;
        hence contradiction by A3,A99,A113;
      end;
      suppose
A114:    y = 21;
        462 = 30*15+12;
        hence contradiction by A3,A99,A114,NAT_4:9;
      end;
      suppose
A115:    y = 22;
        506 = 30*16+26;
        hence contradiction by A3,A99,A115,NAT_4:9;
      end;
      suppose
A116:    y = 23;
        6 divides 6*4;
        hence contradiction by A3,A99,A116;
      end;
      suppose
A117:    y = 24;
        6 divides 6*4;
        hence contradiction by A3,A99,A117;
      end;
      suppose
A118:    y = 25;
        5 divides 5*5;
        hence contradiction by A3,A99,A118;
      end;
      suppose
A119:    y = 26;
        702 = 30*23+12;
        hence contradiction by A3,A99,A119,NAT_4:9;
      end;
      suppose
A120:    y = 27;
        756 = 30*25+6;
        hence contradiction by A3,A99,A120,NAT_4:9;
      end;
      suppose
A121:    y = 28;
        812 = 30*27+2;
        hence contradiction by A3,A99,A121,NAT_4:9;
      end;
      suppose
A122:    y = 29;
        5 divides 5*6;
        hence contradiction by A3,A99,A122;
      end;
      suppose
A123:    y = 30;
        5 divides 5*6;
        hence contradiction by A3,A99,A123;
      end;
      suppose
A124:    y = 31;
        992 = 30*33+2;
        hence contradiction by A3,A99,A124,NAT_4:9;
      end;
      suppose
A125:    y = 32;
        1056 = 30*35+6;
        hence contradiction by A3,A99,A125,NAT_4:9;
      end;
      suppose
A126:    y = 33;
        1122 = 30*37+12;
        hence contradiction by A3,A99,A126,NAT_4:9;
      end;
      suppose
A127:    y = 34;
        5 divides 5*7;
        hence contradiction by A3,A99,A127;
      end;
    end;
    suppose
A128:  x = 6;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A128,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A128,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A128,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A128,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A128;
      end;
      suppose y = 6;
        hence contradiction by A3,A128;
      end;
      suppose y = 7;
        hence contradiction by A3,A128;
      end;
      suppose
A129:    y = 8;
        72 = 42*1+30;
        hence contradiction by A3,A128,A129,NAT_4:9;
      end;
      suppose
A130:    y = 9;
        90 = 42*2+6;
        hence contradiction by A3,A128,A130,NAT_4:9;
      end;
      suppose
A131:    y = 10;
        110 = 42*2+26;
        hence contradiction by A3,A128,A131,NAT_4:9;
      end;
      suppose
A132:    y = 11;
        6 divides 6*2;
        hence contradiction by A3,A128,A132;
      end;
      suppose
A133:    y = 12;
        6 divides 6*2;
        hence contradiction by A3,A128,A133;
      end;
      suppose
A134:    y = 13;
        7 divides 7*2;
        hence contradiction by A3,A128,A134;
      end;
      suppose
A135:    y = 14;
        7 divides 7*2;
        hence contradiction by A3,A128,A135;
      end;
      suppose
A136:    y = 15;
        240 = 42*5+30;
        hence contradiction by A3,A128,A136,NAT_4:9;
      end;
      suppose
A137:    y = 16;
        272 = 42*6+20;
        hence contradiction by A3,A128,A137,NAT_4:9;
      end;
      suppose
A138:    y = 17;
        6 divides 6*3;
        hence contradiction by A3,A128,A138;
      end;
      suppose
A139:    y = 18;
        6 divides 6*3;
        hence contradiction by A3,A128,A139;
      end;
      suppose
A140:    y = 19;
        380 = 42*9+2;
        hence contradiction by A3,A128,A140,NAT_4:9;
      end;
      suppose
A141:    y = 20;
        7 divides 7*3;
        hence contradiction by A3,A128,A141;
      end;
      suppose
A142:    y = 21;
        7 divides 7*3;
        hence contradiction by A3,A128,A142;
      end;
      suppose
A143:    y = 22;
        506 = 42*12+2;
        hence contradiction by A3,A128,A143,NAT_4:9;
      end;
      suppose
A144:    y = 23;
        6 divides 6*4;
        hence contradiction by A3,A128,A144;
      end;
      suppose
A145:    y = 24;
        6 divides 6*4;
        hence contradiction by A3,A128,A145;
      end;
      suppose
A146:    y = 25;
        650 = 42*15+20;
        hence contradiction by A3,A128,A146,NAT_4:9;
      end;
      suppose
A147:    y = 26;
        702 = 42*16+30;
        hence contradiction by A3,A128,A147,NAT_4:9;
      end;
      suppose
A148:    y = 27;
        7 divides 7*4;
        hence contradiction by A3,A128,A148;
      end;
      suppose
A149:    y = 28;
        7 divides 7*4;
        hence contradiction by A3,A128,A149;
      end;
      suppose
A150:    y = 29;
        6 divides 6*5;
        hence contradiction by A3,A128,A150;
      end;
      suppose
A151:    y = 30;
        6 divides 6*5;
        hence contradiction by A3,A128,A151;
      end;
      suppose
A152:    y = 31;
        992 = 42*23+26;
        hence contradiction by A3,A128,A152,NAT_4:9;
      end;
      suppose
A153:    y = 32;
        1056 = 42*25+6;
        hence contradiction by A3,A128,A153,NAT_4:9;
      end;
      suppose
A154:    y = 33;
        1122 = 42*26+30;
        hence contradiction by A3,A128,A154,NAT_4:9;
      end;
      suppose
A155:    y = 34;
        7 divides 7*5;
        hence contradiction by A3,A128,A155;
      end;
    end;
    suppose
A156:  x = 7;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A156,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A156,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A156,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A156,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A156,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A156;
      end;
      suppose y = 7;
        hence contradiction by A3,A156;
      end;
      suppose y = 8;
        hence contradiction by A3,A156;
      end;
      suppose
A157:    y = 9;
        90 = 56*1+34;
        hence contradiction by A3,A156,A157,NAT_4:9;
      end;
      suppose
A158:    y = 10;
        110 = 56*1+54;
        hence contradiction by A3,A156,A158,NAT_4:9;
      end;
      suppose
A159:    y = 11;
        132 = 56*2+20;
        hence contradiction by A3,A156,A159,NAT_4:9;
      end;
      suppose
A160:    y = 12;
        156 = 56*2+44;
        hence contradiction by A3,A156,A160,NAT_4:9;
      end;
      suppose
A161:    y = 13;
        7 divides 7*2;
        hence contradiction by A3,A156,A161;
      end;
      suppose
A162:    y = 14;
        7 divides 7*2;
        hence contradiction by A3,A156,A162;
      end;
      suppose
A163:    y = 15;
        8 divides 8*2;
        hence contradiction by A3,A156,A163;
      end;
      suppose
A164:    y = 16;
        8 divides 8*2;
        hence contradiction by A3,A156,A164;
      end;
      suppose
A165:    y = 17;
        306 = 56*5+26;
        hence contradiction by A3,A156,A165,NAT_4:9;
      end;
      suppose
A166:    y = 18;
        342 = 56*6+6;
        hence contradiction by A3,A156,A166,NAT_4:9;
      end;
      suppose
A167:    y = 19;
        380 = 56*6+44;
        hence contradiction by A3,A156,A167,NAT_4:9;
      end;
      suppose
A168:    y = 20;
        7 divides 7*3;
        hence contradiction by A3,A156,A168;
      end;
      suppose
A169:    y = 21;
        7 divides 7*3;
        hence contradiction by A3,A156,A169;
      end;
      suppose
A170:    y = 22;
        506 = 56*9+2;
        hence contradiction by A3,A156,A170,NAT_4:9;
      end;
      suppose
A171:    y = 23;
        8 divides 8*3;
        hence contradiction by A3,A156,A171;
      end;
      suppose
A172:    y = 24;
        8 divides 8*3;
        hence contradiction by A3,A156,A172;
      end;
      suppose
A173:    y = 25;
        650 = 56*11+34;
        hence contradiction by A3,A156,A173,NAT_4:9;
      end;
      suppose
A174:    y = 26;
        702 = 56*12+30;
        hence contradiction by A3,A156,A174,NAT_4:9;
      end;
      suppose
A175:    y = 27;
        7 divides 7*4;
        hence contradiction by A3,A156,A175;
      end;
      suppose
A176:    y = 28;
        7 divides 7*4;
        hence contradiction by A3,A156,A176;
      end;
      suppose
A177:    y = 29;
        870 = 56*15+30;
        hence contradiction by A3,A156,A177,NAT_4:9;
      end;
      suppose
A178:    y = 30;
        930 = 56*16+34;
        hence contradiction by A3,A156,A178,NAT_4:9;
      end;
      suppose
A179:    y = 31;
        8 divides 8*4;
        hence contradiction by A3,A156,A179;
      end;
      suppose
A180:    y = 32;
        8 divides 8*4;
        hence contradiction by A3,A156,A180;
      end;
      suppose
A181:    y = 33;
        1122 = 56*20+2;
        hence contradiction by A3,A156,A181,NAT_4:9;
      end;
      suppose
A182:    y = 34;
        7 divides 7*5;
        hence contradiction by A3,A156,A182;
      end;
    end;
    suppose
A183:  x = 8;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A183,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A183;
      end;
      suppose y = 8;
        hence contradiction by A3,A183;
      end;
      suppose y = 9;
        hence contradiction by A3,A183;
      end;
      suppose
A184:    y = 10;
        110 = 72*1+38;
        hence contradiction by A3,A183,A184,NAT_4:9;
      end;
      suppose
A185:    y = 11;
        132 = 72*1+60;
        hence contradiction by A3,A183,A185,NAT_4:9;
      end;
      suppose
A186:    y = 12;
        156 = 72*2+12;
        hence contradiction by A3,A183,A186,NAT_4:9;
      end;
      suppose
A187:    y = 13;
        182 = 72*2+38;
        hence contradiction by A3,A183,A187,NAT_4:9;
      end;
      suppose
A188:    y = 14;
        210 = 72*2+66;
        hence contradiction by A3,A183,A188,NAT_4:9;
      end;
      suppose
A189:    y = 15;
        8 divides 8*2;
        hence contradiction by A3,A183,A189;
      end;
      suppose
A190:    y = 16;
        8 divides 8*2;
        hence contradiction by A3,A183,A190;
      end;
      suppose
A191:    y = 17;
        9 divides 9*2;
        hence contradiction by A3,A183,A191;
      end;
      suppose
A192:    y = 18;
        9 divides 9*2;
        hence contradiction by A3,A183,A192;
      end;
      suppose
A193:    y = 19;
        380 = 72*5+20;
        hence contradiction by A3,A183,A193,NAT_4:9;
      end;
      suppose
A194:    y = 20;
        420 = 72*5+60;
        hence contradiction by A3,A183,A194,NAT_4:9;
      end;
      suppose
A195:    y = 21;
        462 = 72*6+30;
        hence contradiction by A3,A183,A195,NAT_4:9;
      end;
      suppose
A196:    y = 22;
        506 = 72*7+2;
        hence contradiction by A3,A183,A196,NAT_4:9;
      end;
      suppose
A197:    y = 23;
        8 divides 8*3;
        hence contradiction by A3,A183,A197;
      end;
      suppose
A198:    y = 24;
        8 divides 8*3;
        hence contradiction by A3,A183,A198;
      end;
      suppose
A199:    y = 25;
        650 = 72*9+2;
        hence contradiction by A3,A183,A199,NAT_4:9;
      end;
      suppose
A200:    y = 26;
        9 divides 9*3;
        hence contradiction by A3,A183,A200;
      end;
      suppose
A201:    y = 27;
        9 divides 9*3;
        hence contradiction by A3,A183,A201;
      end;
      suppose
A202:    y = 28;
        812 = 72*11+20;
        hence contradiction by A3,A183,A202,NAT_4:9;
      end;
      suppose
A203:    y = 29;
        870 = 72*12+6;
        hence contradiction by A3,A183,A203,NAT_4:9;
      end;
      suppose
A204:    y = 30;
        930 = 72*12+66;
        hence contradiction by A3,A183,A204,NAT_4:9;
      end;
      suppose
A205:    y = 31;
        8 divides 8*4;
        hence contradiction by A3,A183,A205;
      end;
      suppose
A206:    y = 32;
        8 divides 8*4;
        hence contradiction by A3,A183,A206;
      end;
      suppose
A207:    y = 33;
        1122 = 72*15+42;
        hence contradiction by A3,A183,A207,NAT_4:9;
      end;
      suppose
A208:    y = 34;
        1190 = 72*16+38;
        hence contradiction by A3,A183,A208,NAT_4:9;
      end;
    end;
    suppose
A209:  x = 9;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A209,NAT_D:7;
      end;
      suppose y = 8;
        hence contradiction by A3,A209;
      end;
      suppose y = 9;
        hence contradiction by A3,A209;
      end;
      suppose y = 10;
        hence contradiction by A3,A209;
      end;
      suppose
A210:    y = 11;
        132 = 90*1+42;
        hence contradiction by A3,A209,A210,NAT_4:9;
      end;
      suppose
A211:    y = 12;
        156 = 90*1+66;
        hence contradiction by A3,A209,A211,NAT_4:9;
      end;
      suppose
A212:    y = 13;
        182 = 90*2+2;
        hence contradiction by A3,A209,A212,NAT_4:9;
      end;
      suppose
A213:    y = 14;
        210 = 90*2+30;
        hence contradiction by A3,A209,A213,NAT_4:9;
      end;
      suppose
A214:    y = 15;
        240 = 90*2+60;
        hence contradiction by A3,A209,A214,NAT_4:9;
      end;
      suppose
A215:    y = 16;
        272 = 90*3+2;
        hence contradiction by A3,A209,A215,NAT_4:9;
      end;
      suppose
A216:    y = 17;
        9 divides 9*2;
        hence contradiction by A3,A209,A216;
      end;
      suppose
A217:    y = 18;
        9 divides 9*2;
        hence contradiction by A3,A209,A217;
      end;
      suppose
A218:    y = 19;
        10 divides 10*2;
        hence contradiction by A3,A209,A218;
      end;
      suppose
A219:    y = 20;
        10 divides 10*2;
        hence contradiction by A3,A209,A219;
      end;
      suppose
A220:    y = 21;
        462 = 90*5+12;
        hence contradiction by A3,A209,A220,NAT_4:9;
      end;
      suppose
A221:    y = 22;
        506 = 90*5+56;
        hence contradiction by A3,A209,A221,NAT_4:9;
      end;
      suppose
A222:    y = 23;
        552 = 90*6+12;
        hence contradiction by A3,A209,A222,NAT_4:9;
      end;
      suppose
A223:    y = 24;
        600 = 90*6+60;
        hence contradiction by A3,A209,A223,NAT_4:9;
      end;
      suppose
A224:    y = 25;
        650 = 90*7+20;
        hence contradiction by A3,A209,A224,NAT_4:9;
      end;
      suppose
A225:    y = 26;
        9 divides 9*3;
        hence contradiction by A3,A209,A225;
      end;
      suppose
A226:    y = 27;
        9 divides 9*3;
        hence contradiction by A3,A209,A226;
      end;
      suppose
A227:    y = 28;
        812 = 90*9+2;
        hence contradiction by A3,A209,A227,NAT_4:9;
      end;
      suppose
A228:    y = 29;
        10 divides 10*3;
        hence contradiction by A3,A209,A228;
      end;
      suppose
A229:    y = 30;
        10 divides 10*3;
        hence contradiction by A3,A209,A229;
      end;
      suppose
A230:    y = 31;
        992 = 90*11+2;
        hence contradiction by A3,A209,A230,NAT_4:9;
      end;
      suppose
A231:    y = 32;
        1056 = 90*11+66;
        hence contradiction by A3,A209,A231,NAT_4:9;
      end;
      suppose
A232:    y = 33;
        1122 = 90*12+42;
        hence contradiction by A3,A209,A232,NAT_4:9;
      end;
      suppose
A233:    y = 34;
        1190 = 90*13+20;
        hence contradiction by A3,A209,A233,NAT_4:9;
      end;
    end;
    suppose
A234:  x = 10;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 8;
        hence contradiction by A3,A234,NAT_D:7;
      end;
      suppose y = 9;
        hence contradiction by A3,A234;
      end;
      suppose y = 10;
        hence contradiction by A3,A234;
      end;
      suppose y = 11;
        hence contradiction by A3,A234;
      end;
      suppose
A235:    y = 12;
        156 = 110*1+46;
        hence contradiction by A3,A234,A235,NAT_4:9;
      end;
      suppose
A236:    y = 13;
        182 = 110*1+72;
        hence contradiction by A3,A234,A236,NAT_4:9;
      end;
      suppose
A237:    y = 14;
        210 = 110*1+100;
        hence contradiction by A3,A234,A237,NAT_4:9;
      end;
      suppose
A238:    y = 15;
        240 = 110*2+20;
        hence contradiction by A3,A234,A238,NAT_4:9;
      end;
      suppose
A239:    y = 16;
        272 = 110*2+52;
        hence contradiction by A3,A234,A239,NAT_4:9;
      end;
      suppose
A240:    y = 17;
        306 = 110*2+86;
        hence contradiction by A3,A234,A240,NAT_4:9;
      end;
      suppose
A241:    y = 18;
        342 = 110*3+12;
        hence contradiction by A3,A234,A241,NAT_4:9;
      end;
      suppose
A242:    y = 19;
        10 divides 10*2;
        hence contradiction by A3,A234,A242;
      end;
      suppose
A243:    y = 20;
        10 divides 10*2;
        hence contradiction by A3,A234,A243;
      end;
      suppose
A244:    y = 21;
        11 divides 11*2;
        hence contradiction by A3,A234,A244;
      end;
      suppose
A245:    y = 22;
        11 divides 11*2;
        hence contradiction by A3,A234,A245;
      end;
      suppose
A246:    y = 23;
        552 = 110*5+2;
        hence contradiction by A3,A234,A246,NAT_4:9;
      end;
      suppose
A247:    y = 24;
        600 = 110*5+50;
        hence contradiction by A3,A234,A247,NAT_4:9;
      end;
      suppose
A248:    y = 25;
        650 = 110*5+100;
        hence contradiction by A3,A234,A248,NAT_4:9;
      end;
      suppose
A249:    y = 26;
        702 = 110*6+42;
        hence contradiction by A3,A234,A249,NAT_4:9;
      end;
      suppose
A250:    y = 27;
        756 = 110*6+96;
        hence contradiction by A3,A234,A250,NAT_4:9;
      end;
      suppose
A251:    y = 28;
        812 = 110*7+42;
        hence contradiction by A3,A234,A251,NAT_4:9;
      end;
      suppose
A252:    y = 29;
        10 divides 10*3;
        hence contradiction by A3,A234,A252;
      end;
      suppose
A253:    y = 30;
        10 divides 10*3;
        hence contradiction by A3,A234,A253;
      end;
      suppose
A254:    y = 31;
        992 = 110*9+2;
        hence contradiction by A3,A234,A254,NAT_4:9;
      end;
      suppose
A255:    y = 32;
        11 divides 11*3;
        hence contradiction by A3,A234,A255;
      end;
      suppose
A256:    y = 33;
        11 divides 11*3;
        hence contradiction by A3,A234,A256;
      end;
      suppose
A257:    y = 34;
        1190 = 110*10+90;
        hence contradiction by A3,A234,A257,NAT_4:9;
      end;
    end;
    suppose
A258:  x = 11;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 8;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 9;
        hence contradiction by A3,A258,NAT_D:7;
      end;
      suppose y = 10;
        hence contradiction by A3,A258;
      end;
      suppose y = 11;
        hence contradiction by A3,A258;
      end;
      suppose y = 12;
        hence contradiction by A3,A258;
      end;
      suppose
A259:    y = 13;
        182 = 132*1+50;
        hence contradiction by A3,A258,A259,NAT_4:9;
      end;
      suppose
A260:    y = 14;
        210 = 132*1+78;
        hence contradiction by A3,A258,A260,NAT_4:9;
      end;
      suppose
A261:    y = 15;
        240 = 132*1+108;
        hence contradiction by A3,A258,A261,NAT_4:9;
      end;
      suppose
A262:    y = 16;
        272 = 132*2+8;
        hence contradiction by A3,A258,A262,NAT_4:9;
      end;
      suppose
A263:    y = 17;
        306 = 132*2+42;
        hence contradiction by A3,A258,A263,NAT_4:9;
      end;
      suppose
A264:    y = 18;
        342 = 132*2+78;
        hence contradiction by A3,A258,A264,NAT_4:9;
      end;
      suppose
A265:    y = 19;
        380 = 132*2+116;
        hence contradiction by A3,A258,A265,NAT_4:9;
      end;
      suppose
A266:    y = 20;
        420 = 132*3+24;
        hence contradiction by A3,A258,A266,NAT_4:9;
      end;
      suppose
A267:    y = 21;
        11 divides 11*2;
        hence contradiction by A3,A258,A267;
      end;
      suppose
A268:    y = 22;
        11 divides 11*2;
        hence contradiction by A3,A258,A268;
      end;
      suppose
A269:    y = 23;
        12 divides 12*2;
        hence contradiction by A3,A258,A269;
      end;
      suppose
A270:    y = 24;
        12 divides 12*2;
        hence contradiction by A3,A258,A270;
      end;
      suppose
A271:    y = 25;
        650 = 132*4+122;
        hence contradiction by A3,A258,A271,NAT_4:9;
      end;
      suppose
A272:    y = 26;
        702 = 132*5+42;
        hence contradiction by A3,A258,A272,NAT_4:9;
      end;
      suppose
A273:    y = 27;
        756 = 132*5+96;
        hence contradiction by A3,A258,A273,NAT_4:9;
      end;
      suppose
A274:    y = 28;
        812 = 132*6+20;
        hence contradiction by A3,A258,A274,NAT_4:9;
      end;
      suppose
A275:    y = 29;
        870 = 132*6+78;
        hence contradiction by A3,A258,A275,NAT_4:9;
      end;
      suppose
A276:    y = 30;
        930 = 132*7+6;
        hence contradiction by A3,A258,A276,NAT_4:9;
      end;
      suppose
A277:    y = 31;
        992 = 132*7+68;
        hence contradiction by A3,A258,A277,NAT_4:9;
      end;
      suppose
A278:    y = 32;
        11 divides 11*3;
        hence contradiction by A3,A258,A278;
      end;
      suppose
A279:    y = 33;
        11 divides 11*3;
        hence contradiction by A3,A258,A279;
      end;
      suppose
A280:    y = 34;
        1190 = 132*9+2;
        hence contradiction by A3,A258,A280,NAT_4:9;
      end;
    end;
    suppose
A281:  x = 12;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 8;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 9;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 10;
        hence contradiction by A3,A281,NAT_D:7;
      end;
      suppose y = 11;
        hence contradiction by A3,A281;
      end;
      suppose y = 12;
        hence contradiction by A3,A281;
      end;
      suppose y = 13;
        hence contradiction by A3,A281;
      end;
      suppose
A282:    y = 14;
        210 = 156*1+54;
        hence contradiction by A3,A281,A282,NAT_4:9;
      end;
      suppose
A283:    y = 15;
        240 = 156*1+84;
        hence contradiction by A3,A281,A283,NAT_4:9;
      end;
      suppose
A284:    y = 16;
        272 = 156*1+116;
        hence contradiction by A3,A281,A284,NAT_4:9;
      end;
      suppose
A285:    y = 17;
        306 = 156*1+150;
        hence contradiction by A3,A281,A285,NAT_4:9;
      end;
      suppose
A286:    y = 18;
        342 = 156*2+30;
        hence contradiction by A3,A281,A286,NAT_4:9;
      end;
      suppose
A287:    y = 19;
        380 = 156*2+68;
        hence contradiction by A3,A281,A287,NAT_4:9;
      end;
      suppose
A288:    y = 20;
        420 = 156*2+108;
        hence contradiction by A3,A281,A288,NAT_4:9;
      end;
      suppose
A289:    y = 21;
        462 = 156*2+150;
        hence contradiction by A3,A281,A289,NAT_4:9;
      end;
      suppose
A290:    y = 22;
        506 = 156*3+38;
        hence contradiction by A3,A281,A290,NAT_4:9;
      end;
      suppose
A291:    y = 23;
        12 divides 12*2;
        hence contradiction by A3,A281,A291;
      end;
      suppose
A292:    y = 24;
        12 divides 12*2;
        hence contradiction by A3,A281,A292;
      end;
      suppose
A293:    y = 25;
        13 divides 13*2;
        hence contradiction by A3,A281,A293;
      end;
      suppose
A294:    y = 26;
        13 divides 13*2;
        hence contradiction by A3,A281,A294;
      end;
      suppose
A295:    y = 27;
        756 = 156*4+132;
        hence contradiction by A3,A281,A295,NAT_4:9;
      end;
      suppose
A296:    y = 28;
        812 = 156*5+32;
        hence contradiction by A3,A281,A296,NAT_4:9;
      end;
      suppose
A297:    y = 29;
        870 = 156*5+90;
        hence contradiction by A3,A281,A297,NAT_4:9;
      end;
      suppose
A298:    y = 30;
        930 = 156*5+150;
        hence contradiction by A3,A281,A298,NAT_4:9;
      end;
      suppose
A299:    y = 31;
        992 = 156*6+56;
        hence contradiction by A3,A281,A299,NAT_4:9;
      end;
      suppose
A300:    y = 32;
        1056 = 156*6+120;
        hence contradiction by A3,A281,A300,NAT_4:9;
      end;
      suppose
A301:    y = 33;
        1122 = 156*7+30;
        hence contradiction by A3,A281,A301,NAT_4:9;
      end;
      suppose
A302:    y = 34;
        1190 = 156*7+98;
        hence contradiction by A3,A281,A302,NAT_4:9;
      end;
    end;
    suppose
A303:  x = 13;
      per cases by A5;
      suppose y = 0;
        hence contradiction by A3,NAT_D:6;
      end;
      suppose y = 1;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 2;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 3;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 4;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 5;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 6;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 7;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 8;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 9;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 10;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 11;
        hence contradiction by A3,A303,NAT_D:7;
      end;
      suppose y = 12;
        hence contradiction by A3,A303;
      end;
      suppose y = 13;
        hence contradiction by A3,A303;
      end;
      suppose y = 14;
        hence contradiction by A3,A303;
      end;
      suppose
A304:    y = 15;
        240 = 182*1+58;
        hence contradiction by A3,A303,A304,NAT_4:9;
      end;
      suppose
A305:    y = 16;
        272 = 182*1+90;
        hence contradiction by A3,A303,A305,NAT_4:9;
      end;
      suppose
A306:    y = 17;
        306 = 182*1+124;
        hence contradiction by A3,A303,A306,NAT_4:9;
      end;
      suppose
A307:    y = 18;
        342 = 182*1+160;
        hence contradiction by A3,A303,A307,NAT_4:9;
      end;
      suppose
A308:    y = 19;
        380 = 182*2+16;
        hence contradiction by A3,A303,A308,NAT_4:9;
      end;
      suppose
A309:    y = 20;
        420 = 182*2+56;
        hence contradiction by A3,A303,A309,NAT_4:9;
      end;
      suppose
A310:    y = 21;
        462 = 182*2+98;
        hence contradiction by A3,A303,A310,NAT_4:9;
      end;
      suppose
A311:    y = 22;
        506 = 182*2+142;
        hence contradiction by A3,A303,A311,NAT_4:9;
      end;
      suppose
A312:    y = 23;
        552 = 182*3+6;
        hence contradiction by A3,A303,A312,NAT_4:9;
      end;
      suppose
A313:    y = 24;
        600 = 182*3+54;
        hence contradiction by A3,A303,A313,NAT_4:9;
      end;
      suppose
A314:    y = 25;
        13 divides 13*2;
        hence contradiction by A3,A303,A314;
      end;
      suppose
A315:    y = 26;
        13 divides 13*2;
        hence contradiction by A3,A303,A315;
      end;
      suppose
A316:    y = 27;
        14 divides 14*2;
        hence contradiction by A3,A303,A316;
      end;
      suppose
A317:    y = 28;
        14 divides 14*2;
        hence contradiction by A3,A303,A317;
      end;
      suppose
A318:    y = 29;
        870 = 182*4+142;
        hence contradiction by A3,A303,A318,NAT_4:9;
      end;
      suppose
A319:    y = 30;
        930 = 182*5+20;
        hence contradiction by A3,A303,A319,NAT_4:9;
      end;
      suppose
A320:    y = 31;
        992 = 182*5+82;
        hence contradiction by A3,A303,A320,NAT_4:9;
      end;
      suppose
A321:    y = 32;
        1056 = 182*5+146;
        hence contradiction by A3,A303,A321,NAT_4:9;
      end;
      suppose
A322:    y = 33;
        1122 = 182*6+30;
        hence contradiction by A3,A303,A322,NAT_4:9;
      end;
      suppose
A323:    y = 34;
        1190 = 182*6+98;
        hence contradiction by A3,A303,A323,NAT_4:9;
      end;
    end;
  end;

begin :: Problem 40

theorem Th19:
  a divides b implies n|^a - 1 divides n|^b - 1
  proof
    given m being Nat such that
A1: b = a*m;
    n|^a - 1 divides n|^a|^m - 1|^m by NEWTON01:33;
    hence thesis by A1,NEWTON:9;
  end;

:: Problem 40
theorem
  2|^(2|^n)+1 divides 2|^(2|^(2|^n)+1)-2
  proof
    set A = 2|^(2|^n);
    set F = A+1;
    set G = 2|^(2|^(n+1))-1;
    set H = 2|^A-1;
    set I = 2|^(A+1);
    n+1 <= 2|^n by NEWTON:85;
    then
A1: G divides H by Th19,NEWTON:89;
    (A+1)*(A-1) = A|^2-1|^2 by NEWTON01:1
    .= 2|^(2|^n*2|^1)-1 by NEWTON:9
    .= 2|^(2|^(n+1))-1 by NEWTON:8;
    then F divides G;
    then
A2: F divides H by A1,INT_2:9;
    2|^1*2|^A = I by NEWTON:8;
    then 2*H = I-2;
    then H divides I-2;
    hence F divides 2|^F-2 by A2,INT_2:9;
  end;

begin :: Problem 47

theorem Th21:
  n divides 4 implies n = 1 or n = 2 or n = 4
  proof
    assume
A1: n divides 4;
    then n <= 4 by INT_2:27;
    then
A2: n = 0 or ... or n = 4;
    now
      (3*1+1) mod 3 = 1 mod 3 by NAT_D:21
      .= 1 by NAT_D:24;
      hence not 3 divides 4;
    end;
    hence thesis by A1,A2;
  end;

:: Problem 47
theorem
  n > 6 implies ex a,b being Nat st a > 1 & b > 1 & n = a+b & a,b are_coprime
  proof
    assume
A1: n > 6;
    per cases;
    suppose
A2:   n is odd;
      2 = 2*1;
      then reconsider a = 2 as even Nat;
      reconsider b = n-a as Element of NAT by A1,XXREAL_0:2,INT_1:5;
      take a, b;
      thus a > 1;
      n-a > 6-a by A1,XREAL_1:14;
      hence b > 1 by XXREAL_0:2;
      thus n = a+b;
      2 = 2|^1;
      hence thesis by A2,NAT_5:3;
    end;
    suppose
A3:   n is even;
      consider k such that
A4:   n = 4*k or n = 4*k+1 or n = 4*k+2 or n = 4*k+3 by NUMBER02:24;
      4*k+1 = 2*(2*k)+1 & 4*k+3 = 2*(2*k+1)+1;
      then per cases by A3,A4;
      suppose
A5:     n = 4*k;
A6:     now
          assume 1 >= k;
          then k = 0 or k = 1 by NAT_1:25;
          hence contradiction by A1,A5;
        end;
        then
A7:     2*1 < 2*k by XREAL_1:68;
        then reconsider a = 2*k-1 as odd Element of NAT by INT_1:5,XXREAL_0:2;
        reconsider b = 2*k+1 as odd Element of NAT;
        take a,b;
        2*k-1 > 2-1 by A7,XREAL_1:9;
        hence a > 1;
        1+0 < 2*k+1 by A6,XREAL_1:8;
        hence b > 1;
        thus n = a+b by A5;
        b - a = 2;
        hence thesis by NUMBER03:31;
      end;
      suppose
A8:     n = 4*k+2;
        reconsider a = 2*k+2+1 as Nat;
        4*k+2 > 4+2 by A1,A8;
        then 2*(2*k) > 2*(2*1) by XREAL_1:6;
        then
A9:     2*k > 2*1 by XREAL_1:64;
        then
A10:     1 <= 2*k by XXREAL_0:2;
        then reconsider b = 2*k-1 as Element of NAT by INT_1:5;
        take a,b;
        2*k+3 > 2*k+0 by XREAL_1:8;
        hence a > 1 by A10,XXREAL_0:2;
        2*k-1 > 1+1-1 by A9,XREAL_1:9;
        hence b > 1;
        thus n = a+b by A8;
A11:     1 divides a & 1 divides b by INT_2:12;
        for d being Nat st d divides a & d divides b holds d divides 1
        proof
          let d be Nat such that
A12:      d divides a and
A13:      d divides b;
          d divides a-b by A12,A13,INT_5:1;
          then d = 1 or d = 2*1 or d = 2*2 by Th21;
          hence thesis by A12;
        end;
        hence a gcd b = 1 by A11,NAT_D:def 5;
      end;
    end;
  end;

begin :: Problem 76

definition
  let n be Nat;
  pred n satisfies_Sierpinski_problem_76a means
  for x being Nat st n < x < n+10 holds x is non prime;
end;

definition
  let m be Nat;
  pred m satisfies_Sierpinski_problem_76b means
  for x being Nat st 10*m < x < 10*(m+1) holds x is non prime;
end;

theorem
  113 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 113 < x < 113+10;
    then 113 < x < 122+1;
    then 113+1 <= x <= 122 by NAT_1:13;
    then x = 114 or ... or x = 122;
    hence thesis by XPRIMES0:114,115,116,117,118,119,120,121,122;
  end;

theorem
  114 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 114 < x < 114+10;
    then 114 < x < 123+1;
    then 114+1 <= x <= 123 by NAT_1:13;
    then x = 115 or ... or x = 123;
    hence thesis by XPRIMES0:115,116,117,118,119,120,121,122,123;
  end;

theorem
  115 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 115 < x < 115+10;
    then 115 < x < 124+1;
    then 115+1 <= x <= 124 by NAT_1:13;
    then x = 116 or ... or x = 124;
    hence thesis by XPRIMES0:116,117,118,119,120,121,122,123,124;
  end;

theorem
  116 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 116 < x < 116+10;
    then 116 < x < 125+1;
    then 116+1 <= x <= 125 by NAT_1:13;
    then x = 117 or ... or x = 125;
    hence thesis by XPRIMES0:117,118,119,120,121,122,123,124,125;
  end;

theorem
  117 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 117 < x < 117+10;
    then 117 < x < 126+1;
    then 117+1 <= x <= 126 by NAT_1:13;
    then x = 118 or ... or x = 126;
    hence thesis by XPRIMES0:118,119,120,121,122,123,124,125,126;
  end;

theorem
  139 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 139 < x < 139+10;
    then 139 < x < 148+1;
    then 139+1 <= x <= 148 by NAT_1:13;
    then x = 140 or ... or x = 148;
    hence thesis by XPRIMES0:140,141,142,143,144,145,146,147,148;
  end;

theorem
  181 satisfies_Sierpinski_problem_76a
  proof
    let x be Nat;
    assume 181 < x < 181+10;
    then 181 < x < 190+1;
    then 181+1 <= x <= 190 by NAT_1:13;
    then x = 182 or ... or x = 190;
    hence thesis by XPRIMES0:182,183,184,185,186,187,188,189,190;
  end;

:: Problem 76 a
theorem
  n satisfies_Sierpinski_problem_76a & n <= 181 implies
  n in {113,114,115,116,117,139,181}
  proof
    assume
A1: n satisfies_Sierpinski_problem_76a;
    assume
A2: n <= 181;
    per cases;
    suppose n <= 99;
      then n = 0 or ... or n = 99;
      hence thesis by A1,XPRIMES1:2,11,19,23,31,37,43,47,53,59,67,73,79,83,89,
      97,101;
    end;
    suppose n > 99;
      then n >= 99+1 & n <= 181 by A2,NAT_1:13;
      then n = 100 or ... or n = 181;
      then n = 113 or n = 114 or n = 115 or n = 116 or n = 117 or
      n = 139 or n = 181
      by A1,XPRIMES1:107,113,127,131,139,149,157,163,167,173,181;
      hence thesis by ENUMSET1:def 5;
    end;
  end;

theorem
  20 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*20 < x < 10*(20+1);
    then 200 < x < 209+1;
    then 200+1 <= x <= 209 by NAT_1:13;
    then x = 201 or ... or x = 209;
    hence thesis by XPRIMES0:201,202,203,204,205,206,207,208,209;
  end;

theorem
  32 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*32 < x < 10*(32+1);
    then 320 < x < 329+1;
    then 320+1 <= x <= 329 by NAT_1:13;
    then x = 321 or ... or x = 329;
    hence thesis by XPRIMES0:321,322,323,324,325,326,327,328,329;
  end;

theorem
  51 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*51 < x < 10*(51+1);
    then 510 < x < 519+1;
    then 510+1 <= x <= 519 by NAT_1:13;
    then x = 511 or ... or x = 519;
    hence thesis by XPRIMES0:511,512,513,514,515,516,517,518,519;
  end;

theorem
  53 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*53 < x < 10*(53+1);
    then 530 < x < 539+1;
    then 530+1 <= x <= 539 by NAT_1:13;
    then x = 531 or ... or x = 539;
    hence thesis by XPRIMES0:531,532,533,534,535,536,537,538,539;
  end;

theorem
  62 satisfies_Sierpinski_problem_76b
  proof
    let x be Nat;
    assume 10*62 < x < 10*(62+1);
    then 620 < x < 629+1;
    then 620+1 <= x <= 629 by NAT_1:13;
    then x = 621 or ... or x = 629;
    hence thesis by XPRIMES0:621,622,623,624,625,626,627,628,629;
  end;

:: Problem 76 b
theorem
  m satisfies_Sierpinski_problem_76b & m <= 62 implies m in {20,32,51,53,62}
  proof
    assume
A1: m satisfies_Sierpinski_problem_76b;
    assume m <= 62;
    then m = 0 or ... or m = 62;
    then m = 20 or m = 32 or m = 51 or m = 53 or m = 62
    by A1,XPRIMES1:2,13,23,31,41,53,61,71,83,97,101,113,127,131,149,151,163,
    173,181,191,211,223,233,241,251,263,271,281,293,307,311,331,347,353,367,
    373,383,397,401,419,421,431,443,457,461,479,487,491,503,521,541,557,563,
    571,587,593,601,613;
    hence thesis by ENUMSET1:def 3;
  end;

begin :: Problem 79

theorem Th33:
  c <> 0 & c < b implies not (a*b+c) / b is integer
  proof
    assume that
A1: c <> 0 and
A2: c < b;
A3: (a*b+c) mod b = c mod b by NAT_D:21;
    c mod b = c by A2,NAT_D:24;
    then not b divides a*b+c by A1,A3;
    hence thesis by A2,WSIERP_1:17;
end;

Lm2:
 not 5/4 is integer
 proof
   1*4+1 = 5;
   hence thesis by Th33;
 end;

theorem Th34:
  not ex m,n being positive Nat st m^2 - n^2 = 1
  proof
    given m,n being positive Nat such that
A1: m^2 - n^2 = 1;
A2: now
      assume m^2 <= n^2;
      then m^2 - n^2 <= n^2 - n^2 by XREAL_1:9;
      then m^2 - n^2 <= 0;
      hence contradiction by A1;
    end;
A3: sqrt(1+n*n) <= sqrt 1 + sqrt (n^2) by SQUARE_1:59;
    sqrt(m^2) = m & sqrt(n^2) = n by SQUARE_1:def 2;
    then m < 1+n or m = 1+n by A1,A3,XXREAL_0:1,SQUARE_1:18;
    then per cases by NAT_1:13;
    suppose m <= n;
      hence thesis by A2,SQUARE_1:15;
    end;
    suppose m = 1+n;
      then (1+n)^2 - n^2 = 1 by A1;
      then 2*n = 0;
      hence thesis;
    end;
  end;

theorem Th35:
  not ex m,n being positive Nat st m^2 - n^2 = 4
  proof
    given m,n being positive Nat such that
A1: m^2 - n^2 = 4;
    now
      assume m^2 <= n^2;
      then m^2 - n^2 <= n^2 - n^2 by XREAL_1:9;
      then m^2 - n^2 <= 0;
      hence contradiction by A1;
    end;
    then
A2: m > n by SQUARE_1:15;
    per cases;
    suppose m is even;
      then consider a being Nat such that
A3:   m = 2*a;
      per cases;
      suppose n is even;
        then consider b being Nat such that
A4:     n = 2*b;
        4*a*a - 4*b*b = 4 by A1,A3,A4;
        then
A5:     a^2-b^2 = 1;
        a is positive & b is positive by A3,A4;
        hence thesis by A5,Th34;
      end;
      suppose n is odd;
        then consider b being Nat such that
A6:     n = 2*b+1 by ABIAN:9;
        4*a*a - (4*b*b+4*b+1) = 4 by A1,A3,A6;
        then a*a-b*b-b = 5/4;
        hence contradiction by Lm2;
      end;
    end;
    suppose m is odd;
      then consider a being Nat such that
A7:   m = 2*a+1 by ABIAN:9;
      per cases;
      suppose n is even;
        then consider b being Nat such that
A8:     n = 2*b;
        4*a*a+4*a+1 - 4*b*b = 4 by A1,A7,A8;
        then a*a+a-b*b = 3/4;
        hence contradiction by NAT_D:33;
      end;
      suppose n is odd;
        then consider b being Nat such that
A9:     n = 2*b+1 by ABIAN:9;
A10:    4*a*a+4*a+1 - (4*b*b+4*b+1) = 4 by A1,A7,A9;
        2*b+1-1 < 2*a+1-1 by A2,A7,A9,XREAL_1:9;
        then
A11:    b < a by XREAL_1:64;
        then b^2 < a^2 by XREAL_1:96;
        then a^2 - b^2 > b^2 - b^2 by XREAL_1:9;
        then
A12:    a^2 - b^2 >= 0+1 by INT_1:7;
        a - b > b - b by A11,XREAL_1:9;
        then a-b >= 0+1 by INT_1:7;
        then a^2 - b^2 + (a-b) >= 1+1 by A12,XREAL_1:7;
        hence contradiction by A10;
      end;
    end;
  end;

theorem Th36:
  (2*n+1)^2 mod 8 = 1
  proof
    defpred P[Nat] means (2*$1+1)^2 mod 8 = 1;
A1: P[0] by NAT_D:24;
A2: P[k] implies P[k+1]
    proof
      assume
A3:   P[k];
      thus (2*(k+1)+1)^2 mod 8 = (4*k^2+4*k+1 + 8*(k+1)) mod 8
      .= (1 + (8*(k+1) mod 8)) mod 8 by A3,NAT_D:66
      .= (1 + 0) mod 8
      .= 1 by NAT_D:24;
    end;
    P[k] from NAT_1:sch 2(A1,A2);
    hence thesis;
  end;

theorem Th37:
  n is odd implies n^2 mod 8 = 1
  proof
    assume n is odd;
    then ex a st n = 2*a+1 by ABIAN:9;
    hence thesis by Th36;
  end;

Lm3:
  p is odd implies 3 <= p
  proof
    1 < p by INT_2:def 4;
    then 1+1 <= p by NAT_1:13;
    then 2 = p or 2 < p by XXREAL_0:1;
    then 2 = p or 2+1 <= p by NAT_1:13;
    hence thesis;
  end;

Lm4:
  p is odd implies 9 <= p^2
  proof
    assume p is odd;
    then 3 <= p by Lm3;
    then 3*3 <= p*p by XREAL_1:66;
    hence thesis;
  end;

theorem Th38:
  for q,s,t being Prime st q^2 = s^2 + t^2 holds
  s is even & t is odd or s is odd & t is even
  proof
    let q,s,t be Prime such that
A1: q^2 = s^2 + t^2;
    assume s is odd or t is even;
    then per cases;
    suppose
A2:   s is odd;
      now
        assume
A3:     t is odd;
        then q is even by A1,A2;
        then
A4:     q = 2 by LAGRA4SQ:13;
        9 <= s^2 & 9 <= t^2 by A2,A3,Lm4;
        then 9+9 <= s^2 + t^2 by XREAL_1:7;
        hence contradiction by A1,A4;
      end;
      hence thesis by A2;
    end;
    suppose t is even;
      then t = 2 by LAGRA4SQ:13;
      then q^2 - s^2 = 4 by A1;
      hence thesis by Th35;
    end;
  end;

theorem Th39:
  not ex q,s,t being Prime st q^2 = s^2 + t^2
  proof
    given q,s,t being Prime such that
A1: q^2 = s^2 + t^2;
    per cases by A1,Th38;
    suppose that
A2:   s is even and t is odd;
      s = 2 by A2,LAGRA4SQ:13;
      then q^2 - t^2 = 4 by A1;
      hence thesis by Th35;
    end;
    suppose that s is odd and
A3:   t is even;
      t = 2 by A3,LAGRA4SQ:13;
      then q^2 - s^2 = 4 by A1;
      hence thesis by Th35;
    end;
  end;

theorem
  for p,q,r,s,t being Prime st p^2 + q^2 = r^2 + s^2 + t^2 holds
  p is even or q is even or r is even or s is even or t is even;

:: Problem 79
theorem
  not ex p,q,r,s,t being Prime st p^2 + q^2 = r^2 + s^2 + t^2
  proof
    given p,q,r,s,t being Prime such that
A1: p^2 + q^2 = r^2 + s^2 + t^2;
A2: now
      assume p = r;
      then p^2 + q^2 = p^2 + (s^2 + t^2) by A1;
      hence contradiction by Th39;
    end;
A3: now
      assume p = s;
      then p^2 + q^2 = p^2 + (r^2 + t^2) by A1;
      hence contradiction by Th39;
    end;
A4: p <> t by A1,Th39;
A5: now
      assume q = r;
      then p^2 + q^2 = q^2 + (s^2 + t^2) by A1;
      hence contradiction by Th39;
    end;
A6: now
      assume q = s;
      then p^2 + q^2 = q^2 + (r^2 + t^2) by A1;
      hence contradiction by Th39;
    end;
A7: q <> t by A1,Th39;
A8: (p^2 + q^2) mod 8 = ((p^2 mod 8) + (q^2 mod 8)) mod 8 by NAT_D:66;
A9: (r^2 + s^2) mod 8 = ((r^2 mod 8) + (s^2 mod 8)) mod 8 by NAT_D:66;
A10: (r^2 + s^2 + t^2) mod 8 = ((r^2 + s^2) mod 8 + (t^2 mod 8)) mod 8
    by NAT_D:66;
A11: 2^2 mod 8 = 4 by NAT_D:24;
    per cases;
    suppose p is even or q is even;
      then
A12:   p = 2 or q = 2 by LAGRA4SQ:13;
      then
A13:   r is odd by A2,A5,LAGRA4SQ:13;
      then
A14:  r^2 mod 8 = 1 by Th37;
A15:  s is odd by A3,A6,A12,LAGRA4SQ:13;
      then
A16:  s^2 mod 8 = 1 by Th37;
A17:  t is odd by A4,A7,A12,LAGRA4SQ:13;
      then
A18:  t^2 mod 8 = 1 by Th37;
A19:  p is even implies q is odd by A1,A13,A15,A17;
A20:  (p^2 + q^2) mod 8 = (1 + 4) mod 8 by A8,A12,A11,A19,Th37
      .= 5 by NAT_D:24;
      (r^2 + s^2 + t^2) mod 8 = (2+1) mod 8 by A9,A10,A16,A18,A14,NAT_D:24
      .= 3 by NAT_D:24;
      hence contradiction by A1,A20;
    end;
    suppose
A21:  p is odd & q is odd;
      then p^2 mod 8 = 1 & q^2 mod 8 = 1 by Th37;
      then
A22:  (p^2 + q^2) mod 8 = 2 by A8,NAT_D:24;
      per cases by A1,A21;
      suppose that
A23:    r is even and
A24:    s is odd;
        t is odd by A1,A21,A23,A24;
        then
A25:    t^2 mod 8 = 1 by Th37;
A26:    s^2 mod 8 = 1 by A24,Th37;
        r = 2 by A23,LAGRA4SQ:13;
        then (r^2 + s^2) mod 8 = 5 by A9,A11,A26,NAT_D:24;
        hence thesis by A1,A22,A10,A25,NAT_D:24;
      end;
      suppose that
A27:    r is even and
A28:    t is even;
        s is even by A1,A21,A27,A28;
        then
A29:    s = 2 by LAGRA4SQ:13;
A30:    t = 2 by A28,LAGRA4SQ:13;
        r = 2 by A27,LAGRA4SQ:13;
        then (r^2 + s^2) mod 8 = 0 by A29,NAT_D:25;
        hence thesis by A1,A22,A10,A30,NAT_D:24;
      end;
      suppose that
A31:    s is even and
A32:    t is odd;
        r is odd by A1,A21,A31,A32;
        then
A33:    r^2 mod 8 = 1 by Th37;
A34:    t^2 mod 8 = 1 by A32,Th37;
        s = 2 by A31,LAGRA4SQ:13;
        then (r^2 + s^2) mod 8 = 5 by A9,A11,A33,NAT_D:24;
        hence thesis by A1,A22,A10,A34,NAT_D:24;
      end;
      suppose that
A35:    s is even and
A36:    r is even;
        t is even by A1,A21,A35,A36;
        then
A37:    t = 2 by LAGRA4SQ:13;
A38:    s = 2 by A35,LAGRA4SQ:13;
        r = 2 by A36,LAGRA4SQ:13;
        then (r^2 + s^2) mod 8 = 0 by A38,NAT_D:25;
        hence thesis by A1,A22,A10,A37,NAT_D:24;
      end;
      suppose that
A39:    t is even and
A40:    r is odd;
        s is odd by A1,A21,A39,A40;
        then
A41:    s^2 mod 8 = 1 by Th37;
A42:    t = 2 by A39,LAGRA4SQ:13;
        r^2 mod 8 = 1 by A40,Th37;
        hence thesis by A1,A11,A22,A9,A10,A42,A41,NAT_D:24;
      end;
      suppose that
A43:    t is even and
A44:    s is even;
A45:    t = 2 by A43,LAGRA4SQ:13;
A46:    s = 2 by A44,LAGRA4SQ:13;
        r is even by A1,A21,A43,A44;
        then r = 2 by LAGRA4SQ:13;
        then (r^2 + s^2) mod 8 = 0 by A46,NAT_D:25;
        hence thesis by A1,A22,A10,A45,NAT_D:24;
      end;
    end;
  end;