
theorem
  5 is Proth
  proof
A1:  2|^2 = 2|^(1+1) .= 2|^1 * 2 by NEWTON:6 .= 2 * 2;
    reconsider e = 1 as odd Nat by Lm5;
    take e,2;
    thus thesis by A1;
  end;
