A211296 a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 1, 2] as of [3, 1, 3].

1, 3, 9, 25, 69, 190, 525, 1457, 4063, 11384, 32042, 90575, 257063, 732301, 2093325, 6002925, 17264587, 49786402, 143922204, 416980589, 1210571810, 3521070621, 10258832781, 29936167744, 87480549441, 255971381746, 749874535899, 2199178125095, 6456071960467, 18970458745182, 55790160614349

Offset

0,2

Links

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Shalosh B. Ekhad and Doron Zeilberger, Automatic Solution of Richard Stanley's Amer. Math. Monthly Problem #11610 and ANY Problem of That Type, arXiv preprint arXiv:1112.6207, 2011. See subpages for rigorous derivations of g.f., recurrence, asymptotics for this sequence.

Crossrefs

Sequence in context: A103780 A211288 A206727 * A098182 A211300 A211293

Adjacent sequences: A211293 A211294 A211295 * A211297 A211298 A211299

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved