theorem Th38:
  divisors(5|^n,4,3) = {}
  proof
    set A = divisors(5|^n,4,3);
    {} = A
    proof
      thus {} c= A;
      let x be object;
      assume x in A;
      then ex k st x = k & k mod 4 = 3 & k divides 5|^n;
      hence thesis by Th34;
    end;
    hence thesis;
  end;
