已知数列{an}的前n项和为Sn=3/2*n^2-123/2*n,则|a1|+|a2|+……+|a30|=?
设数列{an}的前n项和为sn,已知a1+2a2+3a3+…+nan=(n-1)Sn+2n(n∈N*)
设数列an的前n项和为Sn 已知a1+2a2+3a3+……+nan=(n-1)Sn+2n
已知数列an满足a1+2a2+3a3+……+nan=n(n+1)(n+2),则它的前n项和Sn=?
已知数列{an}的前n项和为Sn,且a1+2a2+3a3+…+nan=(n-1)Sn+2n(n∈N*),求数列{an}通
已知数列an满足a1+2a2+3a3+...+nan=n(n+1)*(n+2),则数列an的前n项和Sn=?
已知数列an的前n项和为Sn=n^2+2n,求和:1/(a1*a2)+1/(a2*a3)+...+1/(an*a(n+1
设数列{an}的前n项和为Sn,已知a1+2a2+3a3+…+nan=(n-1)Sn+2n (n∈N*).
已知数列{an}的前n项和为Sn,且 a1+2a2+3a3+…+nan=(n-1)Sn+2n(n∈N*).
已知数列an的前n项和为sn,且sn+an=1/2(n2+5n+2)(2属于n*) 计算a1 a2 a3 a4
数列{an}的前n项和为Sn=10n-n^2,an=-2n+11(n∈N*),若Hn=|a1|+|a2|+...+|an
已知数列{an}的前n项和为Sn,a1=1/2,Sn=n的平方*an,求a1,a2,
已知数列{an}的前n项和sn=n^2+2n+3,求和1/a1+a2+1/a2+a3+1/a3+a4+.+1/an+an