A211284 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 [1, 2, 2].

1, 3, 9, 25, 70, 197, 554, 1563, 4416, 12502, 35463, 100783, 286965, 818614, 2339534, 6698297, 19211785, 55197778, 158857016, 457932482, 1322162806, 3823263357, 11071998176, 32109724225, 93248516464, 271155229971, 789479244108, 2301369264646, 6716318395056, 19622420290276, 57388871934035

Offset

0,2

Links

Table of n, a(n) for n=0..30.

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: A211285 A333498 A097861 * A211283 A333608 A058719

Adjacent sequences: A211281 A211282 A211283 * A211285 A211286 A211287

Keyword

nonn

Author

N. J. A. Sloane, Apr 07 2012

Status

approved