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%I #10 Mar 03 2017 19:41:26
%S 1,3,9,25,71,203,585,1689,4881,14113,40839,118287,342951,995303,
%T 2891309,8406925,24466555,71267575,207771209,606238465,1770339721,
%U 5173862121,15132414675,44292151875,129736008621,380276585553,1115408929215,3273817075159,9615035204811,28256221883283,83087327433025
%N 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 [3, 1, 1].
%H Shalosh B. Ekhad and Doron Zeilberger, <a href="http://arxiv.org/abs/1112.6207">Automatic Solution of Richard Stanley's Amer. Math. Monthly Problem #11610 and ANY Problem of That Type</a>, arXiv preprint arXiv:1112.6207, 2011. See subpages for rigorous derivations of g.f., recurrence, asymptotics for this sequence.
%K nonn
%O 0,2
%A _N. J. A. Sloane_, Apr 07 2012