A211285 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, 2].

1, 3, 9, 25, 70, 196, 551, 1552, 4378, 12375, 35048, 99449, 282724, 805270, 2297862, 6568973, 18812535, 53970516, 155098263, 446456103, 1287215347, 3717084781, 10750037534, 31135125908, 90302734611, 262263047834, 762667932842, 2220610609034, 6473281230694, 18891595418225, 55192784447111

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: A291594 A007046 A211286 * A333498 A097861 A211284

Adjacent sequences: A211282 A211283 A211284 * A211286 A211287 A211288

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved