A211301 a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 2, 3] as of [2, 3, 1].

1, 3, 9, 25, 71, 203, 579, 1659, 4761, 13683, 39399, 113617, 328141, 949123, 2749119, 7973617, 23157121, 67337563, 196043189, 571406485, 1667307271, 4870143753, 14239758879, 41675219715, 122080952361, 357926363463, 1050260357829, 3084183651309, 9063723857271, 26655094384653, 78441446368179

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: A211287 A211290 A211299 * A211295 A211289 A211292

Adjacent sequences: A211298 A211299 A211300 * A211302 A211303 A211304

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved