Forum now runs discourse-math plugin which allows LaTeX-like math.
Simple inline math like \sqrt{n+1} can be written in with $\sqrt{n+1}$
Display-mode math can be written like follows (Note: dollar-signs must on their own lines):
$$
\sum^{\infty}_{n=1} \frac{1}{n}
$$
Which will show up as
\sum^{\infty}_{n=1} \frac{1}{n}
Please give it a shot if you write equations with more than few terms, and especially if there are combinations of fractions and whatnot.