a 1+a2+……a(n- 1)+an=n^2an

& gt& gta 1+a2+……a(n- 1)=(n^2- 1)an

& gt& gt？ s(n- 1)=(n^2- 1)[sn-s(n- 1)]

& gt& gtsn/s(n- 1)=n^2/(n^2- 1)=n/(n+ 1)*n/(n- 1)

List Lai Yi s (n-1)/s (n-2) = (n-1)/n * (n-1)/(n-2).

Multiplication factor:? ………………

S3/S2=3/4*3/2

S2/S 1=2/3*2/ 1？ What is left after rounding: sn/s1= 2n/(n+1) > > Sn=n/(n+ 1) (where S 1=a 1= 1/2)

Therefore, an = sn-s (n-1) = n/(n+1)-(n-1)/n =1[n * (n+1)].

Just found a simpler one: a1+a2+... a (n-1)+an = n2an.

a 1+a2+……a(n- 1)=(n- 1)^2a(n- 1)？ Subtract two expressions

Get an/a (n-1) = (n-1)/(n+1).