List all integers n such that the sum 2^2 + 3^2 + 4^2 + ... + n^2
equals a prime number.
p&p solutions only.

(In reply to

solution by xdog)

**(n-1)*(2n^2 +5n + 6)/6. **

should be presented as

**(n-1)/6 * (2n^2 +5n + 6) **

to be coherent with defining** **(n-1)/6** **as the 1st factor