A051623 Sum (x^2 - n), for x=1+[sqrt(n)] to [sqrt(2n)].

0, 0, 1, 0, 4, 3, 2, 1, 7, 6, 5, 4, 15, 13, 11, 9, 8, 7, 23, 21, 19, 17, 15, 13, 35, 33, 31, 29, 27, 25, 23, 21, 50, 47, 44, 41, 39, 37, 35, 33, 71, 68, 65, 62, 59, 56, 53, 50, 47, 45, 92, 89, 86, 83, 80, 77, 74, 71, 68, 65, 122, 118, 114