MathWrite¶
http://docs.mathjax.org/en/latest/start.html#mathjax-cdn
https://github.com/holidayworking/redmine_latex_mathjax
Anywhere on a wiki page write for inline formulas (inlineMath):
$\sum_i x_i$
and for block type formulas (displayMath):
$$\sum_i x_i$$