a1=1,Sn=n^2an,求an

a1=1,Sn=n^2an,求an a1=1/2,Sn=n^2an-n(n-1),求Sn和an a1=1/2,an+1=an/an+2,求n/an的sn 数列an满足a1=1/3,Sn=n(2n-1)an,求an 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中,a1=-2,an+1=Sn(n∈N+),求an和Sn的表达式 Sn=2an+n a1=1 求an其中{an}的前N项和为Sn a1=1/2,an+1=an/an+2,求n/an的前n项和sn 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 已知数列an中 a1=-2且an+1=sn（n+1为下标）,求an,sn 已知数列{an}满足:a1=3,an=Sn-1+2n,求数列an及sn 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 在数列{an}中,a1=2,an=2an-1+2^n+1 求an和Sn