Posted by haifeng on 2012-05-04 18:39:14 last update 2012-05-04 18:39:14 | Answers (0) | 收藏
若记 $a_n(k)=1^n+2^n+3^n+\cdots+k^n$, 则熟知有
\[a_1(k)=1+2+3+\cdots+k=\frac{1}{2}k(k+1)\]
