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, 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

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