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A211299 a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 2, 1] as of [2, 1, 3]. 0
1, 3, 9, 25, 71, 202, 576, 1643, 4694, 13434, 38512, 110577, 317977, 915753, 2641181, 7628464, 22063605, 63899510, 185302479, 538032124, 1564079757, 4552119931, 13263345605, 38686346248, 112955785122, 330131225222, 965769993745, 2827820620683, 8287119688355, 24305919832796, 71344558858211 (list; graph; refs; listen; history; text; internal format)
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: A101168 A211287 A211290 * A211301 A211295 A211289

Adjacent sequences:  A211296 A211297 A211298 * A211300 A211301 A211302

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Apr 07 2012

STATUS

approved

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Last modified January 26 15:18 EST 2022. Contains 350599 sequences. (Running on oeis4.)