A199639 Indices of hexagonal numbers that are not the difference of two positive hexagonal numbers.

1, 2, 3, 4, 6, 7, 8, 12, 16, 19, 22, 24, 28, 31, 32, 43, 48, 64, 76, 79, 96, 103, 112, 128, 139, 142, 163, 166, 184, 192, 199, 211, 223, 256, 262, 268, 271, 283, 304, 307, 316, 331, 352, 367, 376, 379, 384, 412, 439, 448, 454, 463, 496, 499, 512, 526, 547

Offset: 1

Author

T. D. Noe, Dec 06 2011

Keywords

• nonn

Crossrefs

Cf. A000384 (hexagonal numbers), A135768 (pentagonal case).

Programs

Mathematica

Select[Range[600], Reduce[#*(2*#-1) == x*(2*x-1) - y*(2*y-1) && x > 0 && y > 0, {x, y}, Integers] == False &]