等差数列前n项和为Sn=1/2(An+1/An),求通项An

已知数列{an}中,a2=2,前n项和为Sn,且Sn=n(an+1)/2证明数列{an+1-an}是等差数列 设数列an的前n项和为Sn,a1=1,an=(Sn/n)+2(n-1)(n∈N*) 求证:数列an为等差数列, 已知等差数列an前n项和为Sn,Sn=n^2,求和1/(a1a2)+1/(a2a3)+.+1/[(an-1an] (n≥ 等差数列{an}前n项和为Sn=3n-2n^2,求an 已知等差数列{an}的前n项和为Sn,如果Sn=(an+1/2)^2(n∈N+0,bn=(-1)^n*Sn 数列{an}中,a2=2,前n项和为sn,且sn=n(an+1)/2 证明{a-an}是等差数列 等差数列{an}的前n项和为Sn,且a10=30,a20=50 (1)求通项an（2）若Sn=242求n 已知数列{an}的前n项和为Sn,且满足an+2Sn*Sn-1=0,a1=1/2.求证：{1/Sn}是等差数列 已知正项数列an的前n项和为Sn,a1=1,（an-2）²=8Sn-1.证明an是等差数列. 求解一道数学题!数列an前n项和为sn ,½,an,sn成等差数列. （1）求an （2）bn=log2a2n 设等差数列{an}的前n项和为Sn.已知a4=14 .S10=185.(1)求等差数列{an}的通项公式an.(2) 将 已知公差不为0的等差数列{An}的首项A1=1,前n项和为Sn,若数列{Sn/An}是等差数列,求An?