Helanic Abyss

-problem: 高精度乘方求和(Power Sum)
solution: 用Sp(n)的二重和(double series solution)展开形式.
----link: http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1864
----code: http://docs.google.com/document/pub?id=1tFlPaaZwzEyJpAM-0mpu0Ubd6RBuxzfy3yn2IwnhsiQ

Sp(n)的二重和(double series solution)展开式:

Sp(n)=sum{sum{(-1)^j*(i-j)^p*C(n+p-i+1,n-i)*C(p+1,j)|j=0~i-1}|i=1~p}

把第一个组合数变换一下, 其实没有想象的那么大.

Sp(n)=sum{sum{(-1)^j*(i-j)^p*C(n+p-i+1,p+1)*C(p+1,j)|j=0~i-1}|i=1~p}

参见Power Sum: http://mathworld.wolfram.com/PowerSum.html

话说比赛的时候出这种题目有意思吗…

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