Conditions for changing the order of summation in $ \sum_{i=1}^\infty \sum_{j=1}^\infty a_{ij}$
Does $\sum_{m=1}^{\infty}\sum_{n=1}^{\infty}a_{mn}^3=\sum_{n=1}^{\infty}\sum_{m=1}^{\infty}a_{mn}^3$ occur here?