1. ## Double series

May be you want to give it a try to this nice problem.

Evaluate $\sum\limits_{m = 1}^\infty {\sum\limits_{n = 1}^\infty {\frac{1}
{{m^2 n + mn^2 + 2mn}}} } .$

Cheers

2. Any takers? (It's not hard )

3. Sorry. It is old thread, But really I want to know how to solve this.