Definition:Summation/Propositional Function/Iverson's Convention

Definition
Let $\displaystyle \sum_{R \left({j}\right)} a_j$ be the summation over all $a_j$ such that $j$ satisfies $R$.

This can also be expressed:
 * $\displaystyle \sum_{j \mathop \in \Z} a_j \left[{R \left({j}\right)}\right]$

where $\left[{R \left({j}\right)}\right]$ is Iverson's convention.