已知Sn是等差数列{an}的前n项和,若a2+a4+a15是一个确定的常数,则数列{Sn}中是常数的项是A.S7 B.S8 C.S11 D.S13

已知等差数列{an}中,Sn是它的前n项和,若S16>0,S17 已知等差数列{an}中,Sn是它的前n项和,若S16>0,S17 (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Sn是等差数列{An}的前n项和,S10>0并且S11=0,若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 设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 已知sn=32n-n^2求等差数列|an|的前n项和sn 已知等差数列{an}的前n项和是sn=32n一n*n,求{|an|}的前n项和sn 等差数列an的前n项和是sn,已知s14>0,s15 等差数列{an}的前n项和是Sn,已知S14>0,S15 已知数列{an}的前n项和为Sn=n^2-3n,求证：数列{an}是等差数列 已知数列{an}的前n项和Sn=100n-n^2,证明{an}是等差数列 已知数列｛an｝的前n项和sn=n方+3n,求证数列{an}是等差数列 已知an是等差数列,前n项和为Sn,求证:S3n=3(S2n-Sn) 已知等差数列{an} 的前n项和为Sn,若S12>0,S13 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 已知等差数列的前n项和An=n^2-17n.即便Sn最小的n值是