reserve a, b, n for Nat,
  r for Real,
  f for FinSequence of REAL;
reserve p for Prime;

theorem Th33:
  for x being set st x in dom pfexp n holds x is Prime
proof
  let x be set;
  assume x in dom pfexp n;
  then x in SetPrimes by PARTFUN1:def 2;
  hence thesis by NEWTON:def 6;
end;
