A211282 a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 1, 1] as of [1, 1, 2].

1, 3, 9, 25, 72, 206, 591, 1695, 4868, 13992, 40254, 115910, 334061, 963651, 2782289, 8040281, 23255445, 67322421, 195062233, 565667619, 1641798752, 4769187284, 13865312394, 40343201394, 117479128677, 342369174063, 998540774477, 2914523308557, 8513202922632, 24884854518614, 72792506284329

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: A079857 A265940 A309104 * A211298 A138574 A101499

Adjacent sequences: A211279 A211280 A211281 * A211283 A211284 A211285

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved