实验

\begin{align}\left \lbrace \sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6} \right\rbrace\tag{1.2}\end{align} \begin{align}a^2+b^2&=c^2\\\beta^2&=\sum_{n=0}^{\infty}{\frac{1}{n}}+\int_0^1{\frac{x}{e^x-1}dx}\end{align}