A211286 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 [2, 1, 3].

1, 3, 9, 25, 70, 195, 545, 1526, 4284, 12056, 34013, 96195, 272718, 775011, 2207557, 6302309, 18031941, 51702239, 148548283, 427644891, 1233449265, 3564068374, 10316244428, 29909714061, 86852526228, 252579033621, 735567723900, 2144990584607, 6262870100183, 18307786519038, 53577582619466

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: A244934 A291594 A007046 * A211285 A333498 A097861

Adjacent sequences: A211283 A211284 A211285 * A211287 A211288 A211289

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved