数列1/6,-1/3,9/20,-8/15,25/42的通项公式

问题描述:

数列1/6,-1/3,9/20,-8/15,25/42的通项公式

1/6,-1/3,9/20,-8/15,25/42
1/6,-4/12,9/20,-16/30,25/42
1^2/(2*3),-2^2/(3*4),3^2/(4*5),-4^2/(5*6),5^2/(6*7)
an=(-1)^(n+1)*n^2/[(n+1)(n+2)]