1、an前n项和为sn,sn=2n^2+1,求an2、数列{an}满足sn=1+1/4*an,求an 3、数列{an}满足an=3（n=1）且an=a1+a2+…+an-1(n>=2),求通项4、对任意x属于R,f(x)+f(1-x)=1/2,则f(0)+f(1/n)+f(2/n)+...+f[(n-1)/n]+f(1)=_____5、一个首项为

数列{an}前n项和为Sn,且2Sn+1=3an,求an及Sn 已知数列 an前n项和为Sn,a1=1,Sn=2a(n+1),求Sn 已知数列{an}的前n项和为Sn,an+Sn=2,（n 已知数列{an}的前n项和为Sn,若a1=1/2,Sn=n^2an-n(n-1)求Sn,an 数列{an},an=1/[n*2^(n-1)].前N项和为Sn,求证Sn Sn为等比数列{an}前n项和,an=(2n-1)*3的n次方,求Sn 数列{an}前n项和为Sn,且an+Sn=-2n-1 证明{an+2}是等比数列 Sn=2an+n a1=1 求an其中{an}的前N项和为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 数列An的前n项和为Sn,已知A1=1,An+1=Sn*(n+2)/n,证明数列Sn/n是等比数列 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 数列{an}前n项和为Sn,对一切正整数n都有Sn=n+(1/2)an,求an,Sn an=（2^n-1）/2^（n-1）前n项和为Sn,求Sn 数列an ,a1=1,前n项和为Sn ,正整数n对应的n an Sn 成等差数列.1.证明{Sn+n+2}成等比数列,2.求{n+2/n(n+1)(1+an)}前n项和 已知:sn为数列{an}的前n项和,sn=n^2+1,求通项公式an. 已知等差数列{an}的前n项和为Sn,如果Sn=(an+1/2)^2(n∈N+0,bn=(-1)^n*Sn已知等差数列{an}的前n项和Sn,如果Sn=(an+1/2)^2(n∈N+0,bn=(-1)^n*Sn,试求{bn}的前n项和Tn An=2An-1+2^n+2,n》2,A1=2,Sn为数列{An}的前N项和,证明Sn>n^3+n^2 已知an=n/(n+1),bn=an+1/an,bn的前n项和为Sn求证：2n＜Sn＜2n+1