*Problem #17*

##
For which values of n is it possible to split the sum 1^2+2^2+3^2+...+n^2
into two equal sums? For example 1^2+2^2+3^2 cannot be split into two equal
sums, but 1^2+2^2+...+7^2 can be split into 1^2+2^2+4^2+7^2 and 3^2+5^2+6^2.

Compare to last week's problem.