a1=1,a2=3,a3=7,a4=13,a5=21.求an

问题描述:

a1=1,a2=3,a3=7,a4=13,a5=21.求an
还有一题对所有n>=2,a1*a2*a3=n^2.则√a3+√a5 =

an=n^2-n+1