已知数列{an}满足a1=1 Sn=n² 则a3的值为

已知数列{an}满足:a1=3,an=Sn-1+2n,求数列an及sn 已知数列{an},满足a1=1/2,Sn=n²×an,求an 已知数列{an}满足a1=1/2,sn=n^2an,求通项an 已知数列an满足a1=1/2 sn=n平方×an 求an 已知数列An满足 A1=1/2 Sn=N²An 求An 已知数列an满足a1=1 Sn=2an+n 求an 已知数列an满足a1=1 ,Sn=(n+1)*an/2,求通项 的表达式. 已知数列｛an｝满足a1=1,a（n+1）=sn+（n+1）求：an和sn 已知数列{an}满足a1=1 Sn=n² 则a3的值为 已知数列｛an｝满足a1=1,Sn=n²an.求该数列的通项公式 已知数列an的前n项和sn与通项an满足a1=2,sn+1sn=an+1,求sn 已知数列An的前n项和Sn满足An+2Sn*Sn-1=0,n大于等于2,A1=1/2,求An. 已知数列{an}a1=2前n项和为Sn 且满足Sn Sn-1=3an 求数列{an}的通项公式an已知数列{an}a1=2前n项和为Sn 且满足Sn +Sn-1=3an 求数列{an}的通项公式an 高数,已知数列An满足A1=1／2,且前n项和Sn满足Sn=n²An,则An=? 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 已知数列An满足A1=1／2,且前n项和Sn满足Sn=n²An,则An