Inline math rendering limits underneath instead of besides the sum

Question

I'm here because I'm writing a thesis in LaTeX using overleaf and I'm having some troubles with the math inline style, which is not working. This is what I'm writing:

$p_{nj}^2=\sum\limits_{i\in j}{\left|c_{in}\right|^2}$

and this is what I'm getting:

I know that using the inline math with $...$ the sum should have the limits on its right rather than right over and below it. How could I obtain this effect?

Answer 1

With \limits, you explicitly place them underneath. If you use \sum_{...} you get them, depending on the displaystyle, either besides or underneath:

\documentclass{article}

\usepackage{mathtools}

\begin{document}

$p_{nj}^2=\sum_{i\in j}{\left|c_{in}\right|^2}$

\end{document}