Sequence 1 / 2, - 4 / 5,9 / 10, - 16 / 17,25 / 26 A general term formula of

Sequence 1 / 2, - 4 / 5,9 / 10, - 16 / 17,25 / 26 A general term formula of

(-1)^(n+1) *n²/n²+1