设数列an的前n项和为Sn,若Sn=a1(3的n次方-1)/2(对于所有的n大于等于1）,且a4=54

设数列{an}的前n项和为Sn,若a1=1,Sn=2an+Sn+(n∈N+),则a6= 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 设数列an的首项a1等于1,前n项和为sn,sn+1=2n设数列an的首项a1等于1，前n项和为sn，sn+1=2n 设数列{an}的前n项和为Sn,a1=10,a(n+1)=9Sn+10 设等差数列{an}的前n项和为Sn 若a1=Sn> 设数列an的前n项和为Sn 已知a1=1 na的第n+1次=(n+2)Sn(n属于N正) 证明数列Sn/n是等比数列并求Sn 若数列...设数列an的前n项和为Sn 已知a1=1 na的第n+1次=(n+2)Sn(n属于N正) 证明数列Sn/n是等比数列并求Sn 若 设数列{an}的前n项和为Sn,若对任意正整数,都有Sn=n(a1+an)/2,证明{an}是等差数列. 设数列{an}的前n项和为Sn,若{an}和{根号sn+n}都是公差为d的等差数列,则a1= 设数列的前n项的和为sn,a1=2,根号sn-根号sn-1=根号2,求sn还要求an 设数列前n项和为Sn,Sn-tS(n-1)=n,且a1=1 (1).若数列{an+1}是等比数列,求常数t的值(2){an}的前n项和Sn关 设数列{An}的前n项和为Sn若An+1=3Sn,a1=1则An= (1/2)设数列[an]的前n项和为Sn,已知a1＝1,Sn+1=2Sn+n+1.1,求数列[an]的通项公式.2,若bn=n/an+1-an, 设数列An的前n项和为Sn,已知a1=1,An+1=Sn+3n+1求证数列｛An+3}是等比数列 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 设数列【An】的前n项和为Sn,A1=10,An+1=9Sn+10.设Bn=lgAn,求证数列【Bn】为等差数列 设数列｛an｝的前n项和为sn,若对于所有的正整数n,都有sn=n（a1+an）/2,证明｛an｝是等差数列设数列｛an｝的前n项和为sn,若对于所有的正整数n,都有sn=n（a1+an）/2,证明｛an｝是等差数列 设数列｛an}的前n项和为Sn,已知首项a1=3,且Sn+1+Sn=2an+1,试求此数列的通项公式an及前n项和Sn 设数列{An}的前n项和为Sn若An+1=3Sn,a1=1则a6=