What is the sum of the terms of the following series from 2² to 15² ? 2², 3², 4², 5², ........

The sum of the squares from $1^2$ to $n^2$ is $\frac{n(n+1)(2n+1)}{6}$; for $n=15$ it is $\frac{15\times16\times31}{6}=1240$. The series starts at $2^2$, so $1^2=1$ must be subtracted, leaving 1239. The figure 1240 wrongly includes $1^2$.