
theorem
  17 is Proth
  proof
A1: 2|^2 = 2|^(1+1) .= 2|^1 * 2 by NEWTON:6 .= 2 * 2;
A2: 2|^3 = 2|^(2+1) .= 2|^2 * 2 by NEWTON:6 .= 8 by A1;
A3:  2|^4 = 2|^(3+1) .= 2|^3 * 2 by NEWTON:6 .= 16 by A2;
    reconsider e = 1 as odd Nat by Lm5;
    take e,4;
    thus thesis by A3;
  end;
