A015710 Least k such that phi(n) * sigma(n) + k^2 is a perfect square, or zero if impossible.

1, 0, 1, 1, 0, 1, 1, 1, 2, 0, 3, 1, 3, 1, 0, 2, 29, 1, 0, 1, 5, 4, 1, 1, 2, 26, 5, 3, 2, 1, 0, 1, 4, 1, 6, 2, 8, 1, 3, 5, 2, 1, 2, 1, 1, 8, 4, 1, 15, 0, 16, 0, 7, 1, 7, 6, 6, 6, 9, 1, 4, 1, 6, 10, 119, 8, 6, 1, 8, 1, 5, 1, 9, 1, 11, 9, 1, 4, 8, 1, 17, 0, 1, 1, 10, 12, 9, 2, 5, 1, 3, 6, 2, 8