A211303 a(n) = number of n-lettered words in the alphabet {1, 2, 3, 4} with as many occurrences of the substring (consecutive subword) [1, 1] as of [1, 2].

1, 4, 14, 51, 186, 681, 2507, 9272, 34450, 128569, 481865, 1813294, 6849679, 25967722, 98778134, 376923683, 1442500626, 5535489345, 21295353521, 82114239566, 317305643893, 1228538872416, 4765221729960, 18513858369501, 72039704814391, 280707788515378, 1095205252459856, 4278094293847005

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: A034743 A096241 A283108 * A247415 A292463 A371870

Adjacent sequences: A211300 A211301 A211302 * A211304 A211305 A211306

Keyword

nonn

Author

N. J. A. Sloane, Apr 08 2012

Status

approved