已知等差数列｛An｝前n项和为Sn,且Sm/Sn=m^2/n^2,m≠n,A1=1,则An

Sn=n(A1+An)/2
Sm/Sn=m(A1+Am) / [n(A1+An)] =m^2/n^2
所以(A1+Am) / (A1+An)=m/n
A1=1 nAm+n=mAn+m
An=A1+(n-1)d
d=2
所以An=2n-1