sn=2*3^n,求an

sn=2*3^n,求an an=n*2^n,求Sn an=2^n+n,求Sn 已知an=(2n+1)*3^n,求Sn 数列{an}前n项和为Sn,且2Sn+1=3an,求an及Sn 数列an满足a1=1/3,Sn=n(2n-1)an,求an 已知数列AN的前N项和SN,SN=2N^2+3n+2,求an Sn为等比数列{an}前n项和,an=(2n-1)*3的n次方,求Sn 等差数列{an}前n项和为Sn=3n-2n^2,求an 数列an,an=(2n-1)+1/【3n(n+1)】,求Sn 数列｛an｝,中,a1=1/3,设Sn为数列｛an｝的前n项和,Sn=n（2n-1）an 求Sn an=n+2^（n-1）,求sn an=3/n（n+1）,求sn an=1an=n+2^（n-1）,求sn an=3/n（n+1）,求sn an=1/（2n+1）（2n-1）求sn a1=1/2,Sn=n^2an-n(n-1),求Sn和an 已知数列前n项和为Sn,且Sn=-2n+3,求an及Sn Sn为数列{an}前n项和,(2n-1)Sn+1-(2n+1)Sn=-4n-3 ,求{an}通项公式 已知数列{an}满足:a1=3,an=Sn-1+2n,求数列an及sn 一道关于数列 已知数列{An}的前n项和为Sn,Sn=3+2An,求An 数列an的前n项和为Sn 且Sn=1-2/3an 求an的极限