To enable math, add a yaml front matter line: mathjax: true. This will trigger the necessary JS to render both inline formulas: $e^{i \pi} + 1 = 0,$ as well as block or display formulas:

\[\begin{align} \sum_{i=1}^N &= 1 + 2 + \cdots + N\\ &= \frac{n(n+1)}{2} \end{align}\]