an interesting problem

[Gerson W. Barbosa]

(05-03-2015 01:50 AM)Don Shepherd Wrote:  I forgot to mention another restriction on the 3-digit number: it must contain 3 unique digits, that is, no repeating digits.

Somehow I've assumed that restriction despite there was no reason to do so, which makes my quick solution completely wrong. In that case 113, 131 and 311 would be one solution. I will pay more attention next time :-)