我为啥这里的 LaTeX 炸了啊，但是在本地是没炸的
\begin{align}
G(x) &= x^{s_i} \sum_{n=0} \binom{n + s_i + r_i - 1}{s_i + r_i - 1} x^n\\
&= \sum_{n=0} \binom{n + s_i + r_i - 1}{s_i + r_i - 1} x^{n + s_i}
\end{align
}
源码
$$
\begin{align}
G(x) &= x^{s_i} \sum_{n=0} \binom{n + s_i + r_i - 1}{s_i + r_i - 1} x^n\\
&= \sum_{n=0} \binom{n + s_i + r_i - 1}{s_i + r_i - 1} x^{n + s_i}
\end{align}
$$
