已知Sn是等差数列｛an｝的前n项和S10＞0 并且S11=0 若Sn≤Sk对n属于N*恒成立 则正整数k构成的集合为

已知数列{An}的前n项和Sn.已知S1.S3.S2.成等差数列,求{An}的公比q 已知数列{an}是等差数列,前n项和为Sn,a3=6,s3=12,求S1+S2+S3+S4+.+Sn的值 Sn是等差数列an的前n项和,若S1=1,S2=4,则an= 等比数列{an}中,前n项和为sn,已知S1,S3,S2成等差数列,求{an}的公比Q.已知a1-a3=3,求sn? 等比数列{an}中,前n项和为sn,已知S1,S3,S2成等差数列,求{an}的公比Q.已知a1-a3=3,求sn?RT. (1)已知数列an的前n项和为sn满足sn=an²+bn,求证an是等差数列(2)已知等差数列an的前n项和为sn,求证数列sn/n也成等差数列 已知sn是公差不为0的等差数列{an}的前n项和,且s1,s2,s4成等比数列,则a1分之a2+a3 已知Sn是公差不为0的等差数列｛an｝的前n项和,若s1,s2,s4,成等比数列,则a3/a1等于多少 等比数列{an}的前n项和为Sn,已知S1,S3,S2成等差数列1 ,求｛an｝的公比q2 ,若a1-a3=3求Sn 等比数列an的前n项和为sn 已知s1 s3 s2成等差数列 求an的公比q 求若a1-a3=3 求sn 已知{an}是等差数列,公差d不等于0,且a1 a3 a13成等比数列,sn是{an}的前n项和,（1）求证s1 s2 s9成...已知{an}是等差数列,公差d不等于0,且a1 a3 a13成等比数列,sn是{an}的前n项和,（1）求证s1 s2 s9成等比数 已知数列{An}的前n项和为Sn,A1=A2=1,bn=nSn+（n+2)An,数列{bn}是公差为d的等差数列,证（A1A2.An)(S1.Sn) 已知数列{an}的前n项和sn满足sn=an^2+bn,求证{an}是等差数列 已知数列an的前n项和Sn,且an>0,n属于N*,an,Sn,an^2成等差数列已知数列an的前n项和Sn,且an>0,n属于N*,,,成等差数列求an,若Tn=1/S1+1/S2+1/S3+...+1/Sn,求Tn 设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 已知数列an是等差数列,其前n项和为Sn,a3=6,求1/S1+1/S2+...+1/Sn 已知sn=32n-n^2求等差数列|an|的前n项和sn 已知数列an是首项为4公比为q的等比数列,sn是其前n项和,且4a1,a5,-2a3成等差数列,求设An=S1+S2+…+Sn,求An请详解