} x^n = \frac{1}{1-x} \end{aligned}
\{a_n\}
,
a_n = (-1)^n
;
\begin{aligned} A(x) & = \sum_{n=0}^...{\infty} (-1)^n x^n = \frac{1}{1+x} \end{aligned}
\{a_n\}
,
a_n = k^n
,
k
为正整数 ;
\begin{aligned...}
组合数相关 :
\{a_n\}
,
a_n = \dbinom{m+n-1}{n}
,
m,n
为正整数 ;
\begin{aligned} A(x) & = \sum_{n=0}^{\...-1}{n}
,
m,n
为正整数 ;
\begin{aligned} A(x) & = \sum_{n=0}^{\infty} (-1)^n \dbinom{m+n-1}{n} x^n = \...frac{1}{{(1+x)}^m} \end{aligned}
\{a_n\}
,
a_n = \dbinom{n+1}{n}
,
n
为正整数 ;
\begin{aligned} A(