My post above still applies. I don't have a way to prove that are the only answers...

jacks

2013-10-01 05:01:40

To friends I have edited by Question.

anonimnystefy

2013-10-01 04:41:09

Hi jacks

3 is the only one in the first 100 000 positive integers. If we allow non-negative integers as well, there are also 0 and 1. Those are the only ones I can find, and I'd say the only ones that are the solutions.