reserve a,b,c,k,m,n for Nat;
reserve i,j,x,y for Integer;
reserve p,q for Prime;
reserve r,s for Real;

theorem
  6n+1_Primes c= SetPrimes
  proof
    let a be object;
    assume a in 6n+1_Primes;
    then ex k st a = 6*k+1 & 6*k+1 is prime;
    hence thesis by NEWTON:def 6;
  end;
