数列an=n2,求Sn
问题描述：
数列an=n2,求Sn
答
你说的应该是平方和的数列吧. 解法如下：a(n)=n^2 = n(n+1) - n ,n(n+1)=[n(n+1)(n+2)-(n-1)n(n+1)]/3, n = [n(n+1) - (n-1)n]/2,a(n) = [n(n+1)(n+2) - (n-1)n(n+1)]/3 - [ n(n+1) - (n-1)n]/2,s(n) = [1*2*3-0 + 2...