a1=3,an=2n+1,Sn=195,求d,n这是个A.P.

a1=1,Sn=n^2an,求an 数列an满足a1=1/3,Sn=n(2n-1)an,求an a1=1/2,Sn=n^2an-n(n-1),求Sn和an an=a1+(n-1)d 和Sn=n(a1+an)/2中an是什么意思? an=a1+(n-1)d 和Sn=n(a1+an)/2中an是什么 Sn=n(2n-1)an,a1=1/3,求an 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 已知数列{an}满足:a1=3,an=Sn-1+2n,求数列an及sn Sn=n（2n-1）an a1=1/3求数列的Sn,an 已知a1=3,an=Sn-1+2^n(n大于等于2）,求an,Sn? 已知a1=3,an=Sn-1+2^n(n大于等于2）,求an,Sn? a1=3,an=Sn-1+2n次方.n大于或等于2.求an和Sn a1=3,an=Sn-1+2的n次方.n大于或等于2.求an和Sn 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}a1=1/3,前n项和Sn与an的关系是Sn=n(2n-1)an,求通项公式an 已知{an}中,a1=1/3,前n项和Sn与an的关系是Sn=n(2n-1)an,求通项公式an. a1=1,an+1=an+3^n-n,求an与sn a1=1/2,an+1=an/an+2,求n/an的sn