设等差数列{an}的前n项和为Sn,若-a2013
设等差数列{an}的前n项和为Sn,若-a2013
设等差数列{an}的首项及公差均是正整数,前n项和为sn,且a1>1,a4>6,s3≤12,则a2013=?
设等差数列 {an}的前n 项和为Sn,若S9>0 ,S10
设等差数列an的前n项和为Sn,若S4>=10,S5
设等比数列{an}的公比为q,前n项和为Sn,若Sn+1,Sn,Sn+2成等差数列,则公比q为( )
设等比数列{an}的公比为q,前n项和为Sn,若Sn+1,Sn,Sn+2成等差数列,则q=?
设数列{an}的前n项和为Sn,若对任意正整数,都有Sn=n(a1+an)/2,证明{an}是等差数列.
设等差数列{an}的前 n项和为Sn,且 Sn=(an+1)^/2(n属于N*)若bn=(-1)nSn,求数列{bn}的
等差数列{An}的前n项和为Sn,若 lim Sn/n方 =2
设等差数列{an}的前n项和为Sn ,且S15>0,a8+a9
设等差数列{an}的前n项和为Sn,且S
设数列{an},{bn}都是等差数列,它们的前n项和分别为sn,Tn