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A211300 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, 3, 2]. 1
1, 3, 9, 25, 69, 191, 531, 1483, 4157, 11691, 32989, 93391, 265211, 755375, 2157529, 6178887, 17740209, 51054977, 147260321, 425638453, 1232663985, 3576358773, 10393851033, 30255220019, 88199249723, 257469332747, 752558722085, 2202270400567, 6451788348341, 18920617731293, 55539921460069 (list; graph; refs; listen; history; text; internal format)
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: A206727 A211296 A098182 * A211293 A211291 A211294

Adjacent sequences:  A211297 A211298 A211299 * A211301 A211302 A211303

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Apr 07 2012

STATUS

approved

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Last modified January 19 22:12 EST 2022. Contains 350466 sequences. (Running on oeis4.)