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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
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 20 15:22 EDT 2018. Contains 316388 sequences. (Running on oeis4.)