A211305 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 [2, 3].

1, 4, 14, 49, 173, 617, 2222, 8076, 29605, 109384, 407059, 1524662, 5743964, 21751969, 82752733, 316107245, 1211853152, 4660656826, 17974865576, 69496877137, 269292154210, 1045525145898, 4066354568134, 15840022855209, 61789766045683, 241338711779257, 943701096216542, 3693967024612846

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: A277084 A071737 A071741 * A316974 A278026 A001894

Adjacent sequences: A211302 A211303 A211304 * A211306 A211307 A211308

Keyword

nonn

Author

N. J. A. Sloane, Apr 08 2012

Status

approved