without latex delimiters the _{i=1} in \sum_{i=1}^n a_n is interpreted as subscript. we support \(...\), \[...\], $$...$$ and \begin{$env}...\end{$env} as latex fragment delimiters.
_{i=1}
\sum_{i=1}^n a_n
\(...\)
\[...\]
$$...$$
\begin{$env}...\end{$env}