This is LaTeX code:
[latex]
\displaystyle \sum_{i\in\omega\cdot 3}(i^3+3^i) = \sum_{i\in\omega}(i^3+3^i) + \sum_{i\in\omega}\big((\omega+i)^3+3^{\omega+i}\big) + \sum_{i\in\omega}\big((\omega\cdot 2+ i)^3+3^{\omega\cdot 2+i}\big)
[/latex]