2*n + 1 ----------- 2 2 n *(n + 1)
(2*n + 1)/((n^2*(n + 1)^2))
n^(-2) - 1/(1 + n)^2
1 1 -- - -------- 2 2 n (1 + n)
1 + 2*n -------------- 2 4 3 n + n + 2*n
(1 + 2*n)/(n^2 + n^4 + 2*n^3)
(1.0 + 2.0*n)/(n^2*(1.0 + n)^2)