sn为等差数列{an}的前n项和,s2=s6,a4=1则a5=

设等差数列An的前n项和为Sn,且S4=4S2,A2n=2An+1 等差数列{an}=2n+1,前n项和为Sn,求1/S1+1/S2+.+1/Sn 等差数列 an的前n项和为sn ,若s2=4,s4=20,则公差d= 等差数列｛an｝的前n项和为sn,若s2=2,s4=10,则s6=? 等差数列｛an｝的前n项和为sn,若s2=2,s4=10,则s6=? sn为等差数列{an}的前n项和,s2=s6,a4=1则a5= Sn为等差数列{an}的前n项和,s2=s6,a4=1,则a5= Sn为等差数列,｛an}的前n项和,S2=S6,a4=1,则a5=________________ 等差数列{an}的前n项和为Sn,若S2=2,S4=10,则S6等于? 等差数列｛an｝的前n项和为Sn,若S2=2,S4=10,则S6等于多少? 等差数列{an }的前n项和为sn,若s2=2,s4=10,则s6等于 等差数列{an}的前n项和为Sn,若S2=2,S6=24,则S4等于 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 设等差数列{an}的前n项和为Sn,a1=3/2,且S1,S2,S4成等差数列,求Sn 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 已知等差数列{an}的前n项和为Sn,且满足S2=6,a3+a4=22,求an与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?