
theorem P136c: :: 2nd Step
  for k being Nat holds
    PrimeDivisors ((2 |^ k) * (2 |^ k - 2) + 1) =
       PrimeDivisors (2 |^ k - 1)
  proof
    let k be Nat;
    PrimeDivisors ((2 |^ k) * (2 |^ k - 2) + 1) =
         PrimeDivisors ((2 |^ k - 1) * (2 |^ k - 1))
      .= PrimeDivisors (2 |^ k - 1) \/ PrimeDivisors (2 |^ k - 1)
             by DivisorsMulti
      .= PrimeDivisors (2 |^ k - 1);
    hence thesis;
  end;
