A049260 Smallest nonnegative value taken on by nx^2 - y^2 for an infinite number of integer pairs (x, y).

0, 1, 2, 0, 1, 2, 3, 4, 0, 1, 2, 3, 1, 5, 6, 0, 1, 2, 2, 4, 3, 2, 7, 8, 0, 1, 2, 3, 1, 5, 3, 7, 8, 9, 10, 0, 1, 2, 3, 4, 1, 6, 2, 7, 5, 5, 11, 12, 0, 1, 2, 3, 1, 2, 6, 7, 3, 1, 2, 11, 1, 13, 14, 0, 1, 2, 2, 4, 5, 5, 7, 8, 1, 1, 11, 3, 7, 14, 15, 16, 0, 1, 2, 3, 1, 2, 6, 7, 1, 9, 3, 7, 3, 5, 14, 15, 1