reserve m, n for Nat;

theorem Th38:
  for n being Nat holds n in SCNAT iff Moebius n <> 0
proof
  let n be Nat;
  hereby
    assume n in SCNAT;
    then n is square-free by Def2;
    hence Moebius n <> 0;
  end;
  assume Moebius n <> 0;
  then n is square-free by Def3;
  hence thesis by Def2;
end;
