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

1,2

Links

Table of n, a(n) for n=1..57.

Mathematica

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

Crossrefs

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

Sequence in context: A029748 A018314 A212216 * A215068 A239011 A070525

Adjacent sequences: A199636 A199637 A199638 * A199640 A199641 A199642

Keyword

nonn

Author

T. D. Noe, Dec 06 2011

Status

approved