The sum of the first n terms of the series $1^2 + 2.2^2 + 3^2 + 2.4^2 + 5^2 + 2.6^2+...$ is $\frac{n(n+1)^2}{2}$ when $n$ is even. When $n$ is odd the sum is

Question

( A ) $\frac{n(n+1)^2}{4}$
( B ) $\frac{n^2 (n+1)}{2}$
( C ) $\frac{3n(n+1)}{2}$
( D ) $[\frac{n(n+1)}{2}]^2$