A231353 Least k>=0 such that n - k^2 is a triangular number, or -1 if no such k exists.
0, 0, 1, 0, 1, 2, 0, 1, -1, 3, 0, 1, 3, -1, 2, 0, 1, 4, -1, 2, -1, 0, 1, -1, 3, 2, 4, -1, 0, 1, 3, 4, 2, -1, -1, 5, 0, 1, -1, 6, 2, -1, 6, -1, 4, 0, 1, -1, -1, 2, 7, 6, 4, 5, 3, 0, 1, 6, -1, 2, -1, 4, -1, -1, 3, 8, 0, 1, -1, -1, 2, 4, 6, -1, 8, 3, -1, 7, 0, 1, 5, 6, 2
Offset: 0
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