reserve d,i,j,k,m,n,p,q,x,k1,k2 for Nat,
  a,c,i1,i2,i3,i5 for Integer;

theorem Th53:
  Fermat(3) = 257
proof
  thus Fermat(3) = 2 |^ (4 + 4) + 1 by POWER:61
    .= 2 |^ 4 * 2 |^ 4 + 1 by NEWTON:8
    .= 257 by POWER:62;
end;
