A211295 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, 1].

1, 3, 9, 25, 71, 203, 585, 1689, 4881, 14113, 40839, 118287, 342951, 995303, 2891309, 8406925, 24466555, 71267575, 207771209, 606238465, 1770339721, 5173862121, 15132414675, 44292151875, 129736008621, 380276585553, 1115408929215, 3273817075159, 9615035204811, 28256221883283, 83087327433025

Offset

0,2

Links

Table of n, a(n) for n=0..30.

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: A211290 A211299 A211301 * A211289 A211292 A291683

Adjacent sequences: A211292 A211293 A211294 * A211296 A211297 A211298

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved