Mathematics - Sequence & Series Question with Solution | TestHub

If the sum of the series $1^2+2\cdot 2^2+3^2+2\cdot 4^2+5^2+$ ... $2.6^2+\dots$ upto $\mathrm{n}$ terms, when $\mathrm{n}$ is even, is $\frac{n(n+1{)}^2}{2}$, then the sum of the series, when $\mathrm{n}$ is odd, is