From the bottom up:
-- Is 27 a counter example ? No. It's divisible by 3 and also by 9 .
-- Is 18 a counter example ? No. It's divisible by 3 and also by 9 .
-- Is 69 a counter example ? Yes ! It's divisible by 3, but not by 9 .
-- Is 63 a counter example ? No. It's divisible by 3 and also by 9 .
