设等差数列{an}满足a3=5，a10=-9．求{an}的前n项和Sn及使得Sn最大时n的值．

设等差数列【An】满足A3=5,A10=-9,求通项公式,前n的和Sn及最大的序号n的值 设等差数列{an}满足a3=5，a10=-9，Sn是数列{an}的前n项和，则Sn的最大值为______． 已知等差数列{an}满足：a3=7，a5+a7=26，{an}的前n项和为Sn．求an及Sn． 已知等差数列{an}满足:a3=7,a1＋a11=26,{an}的前n项和为Sn,求an及Sn 设等差数列{an}的前n项和为Sn，已知a3=5，S3=9． 设数列{an}的前n项和为Sn满足2Sn=an+1-2n+1+1，n∈N*，且a1，a2+5，a3成等差数列． 已知等差数列【an】满足:a3=7,a5+a7=26.【an】的前n项和为Sn.(1)求a4及Sn; 已知等差数列{an}满足a3=7,a5+a7=26{an}的前n项和为Sn求a4及Sn 设数列{an}的前n项和为Sn,满足2Sn=an+1-2^n+1+1,且a1,a2+5.a3成等差数列 设等差数列{an}的前n项和为Sn,a9=17,S3=9,求{an}通项公式及前n项和为Sn 已知等差数列{an}满足a2+a4=4,a3+a5=10,求{an}的通项公式及{an}的前n项和sn 已知等差数列an满足a3=7,a5+a7=26,an的前n项和为sn.1.求an和sn