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A199639 Indices of hexagonal numbers that are not the difference of two positive hexagonal numbers. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 10 12:19 EDT 2020. Contains 336379 sequences. (Running on oeis4.)