Hello Rednest

Define

Check trivial values first.

It works.

works for 1 as well

Now assume that is divisible by 3 for all integer vaule of upto a particular value

I see you attempted to evaluate

So if is divisible by 3 so i as and are divisible by 3 then so is ad infinitum.

Therefore by induction is divisible by for all .

Bobak

Edit: I fixed my solution it is correct now. But this isn't the best method. Galactus post is more useful.