Sn=1/2n∧2+1/2n 求sn/s(n+1)
已知an=1/2n(n+1),求Sn
An=n×2^(n-1),求Sn
an=(2^n-1)n,求Sn
已知an=(2n+1)*3^n,求Sn
a1=1,Sn为an前n项和,Sn-S(n-1)=√Sn-√S(n-1)(n>=2)
已知数列an的首项a1=5,前n项和为Sn,且S(n+1)=2Sn+n+5(n∈N*),求数列{an}的前n项和Sn,设
已知Sn=2+5n+8n^2+…+(3n-1)n^n-1(n∈N*)求Sn
已知等差数列an中,a1=1,前n项和Sn,若S(n+1)/Sn=(4n+2)/(n+1),求an
数列an前n项和为sn,a1=1,2s(n+1)-sn=2.n∈n*.求an的通项公式
(1).Sn=1+2×3+3×7...n(2^n-1),求Sn.
已知Sn=1/2n(n+1),Tn=S1+S2+S3+.+Sn,求Tn.
1+2+3+4+.+n,求Sn