A063772 a(k^2 + i) = k + a(i) for k >= 0 and 0 <= i <= k * 2; a(0) = 0.

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