login
A211290
a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 1, 2] as of [1, 2, 2].
1
1, 3, 9, 25, 71, 201, 573, 1635, 4677, 13399, 38457, 110559, 318375, 918281, 2652687, 7674389, 22234411, 64506957, 187396863, 545090409, 1587454407, 4628463753, 13509904359, 39475258065, 115460419701, 338030276619, 990539965197, 2905111047127, 8527250269257, 25049140759647, 73637161597765
OFFSET
0,2
LINKS
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: A233828 A101168 A211287 * A211299 A211301 A211295
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 07 2012
STATUS
approved