# How to specify the step in sum? [closed]

The traditional sum's step is 1, but what if I want to specify the step to be some integer else?

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This appears to be a notational question rather than a TeX one (thus not really on topic for this site) but the \sum nottaion is used to sum over a set or over an implied list indexed by a range of integers so if you want to sum for example every second item in a list x_i then you just double i when referencing
\sum_{i=1}^n x_{2i}