Sn是等差数列an的前n项和,若S1=1,S2=4,则an=

Sn是等差数列an的前n项和,若S1=1,S2=4,则an= 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 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 设等差数列an前n项和为Sn,S2010-S1=1,S2011=? 在等差数列{an}中,a1=1,Sn是前n项和,且S1,S3,S8成等差数列,求a23+2S23的值(要求详细解答) 等差数列{an}=2n+1,前n项和为Sn,求1/S1+1/S2+.+1/Sn 已知等差数列an的前n项和为Sn,若S3/3-S1=1则数列an的公差为? 已知等比数列{an}的公比为q,前n项和为Sn,若S2011,S2010,S2012成等差数列,且S1=1,则an等于 数列{an}中,a1=1/3,前n项和Sn满足Sn+1-Sn=(1/3)^n+1 (n属于N*).(1).求数列{an}的通项公式an以及前n项和Sn（2）.若S1,t(S1+S2),3(S2+S3)成等差数列,求实数t的值 (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 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 数列an是首项为3公差为2的等差数列其前n项和为Sn求An=1/S1+1/S2+1/S3+...+1/Sn 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? 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) sn是数列an的前n项和 且sn+an=2n+1 求证数列an-2是等比数列 求和s1+s2+L+sn 等比数列{an},前n项和为Sn,若S1,2S2,3S3成等差数列,求{an}的公比 数列{an}中,a1=1/3,前n项和Sn满足S(n+1)-Sn=（1/3）^(n+1) (n∈N*)(1)求数列{an}的通项公式an以及前n项和Sn(2)若S1,t(S1+S2),3(S2+S3)成等差数列,求实数t的值 1.设Sn是正数数列{an}的前n项和,已知数列S1 ^2,S2 ^2,...Sn ^2...是以3为首项,1为公差的等差数列.求{an}通项公式2.已知数列{an}前n项和Sn=2n^2-3n,若bn=an·2^n,求数列{bn}的前n项和Tn.3.已知lgx+lgy=1,Sn=lg x^n+lg(