# Category:Summations

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This category contains results about Summations.
Definitions specific to this category can be found in Definitions/Summations.

Let $R \left({j}\right)$ be a propositional function of $j$.

Then we can write the summation as:

$\displaystyle \sum_{R \left({j}\right)} a_j = \text{ The sum of all$a_j$such that$R \left({j}\right)$holds}$.

If more than one propositional function is written under the summation sign, they must all hold.