Definition:Summation/Propositional Function/Iverson's Convention

Definition
Let $\ds \sum_{\map R j} a_j$ be the summation over all $a_j$ such that $j$ satisfies $R$.

This can also be expressed:
 * $\ds \sum_{j \mathop \in \Z} a_j \sqbrk {\map R j}$

where $\sqbrk {\map R j}$ is Iverson's convention.