
theorem DivSquare:
  for a being Nat holds
    PrimeDivisors (a * a) = PrimeDivisors a
  proof
    let a be Nat;
    PrimeDivisors (a * a) = PrimeDivisors a \/ PrimeDivisors a by DivisorsMulti
      .= PrimeDivisors a;
    hence thesis;
  end;
