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%I #12 Sep 10 2020 20:20:56
%S 1,3,9,25,71,203,579,1659,4761,13683,39399,113617,328141,949123,
%T 2749119,7973617,23157121,67337563,196043189,571406485,1667307271,
%U 4870143753,14239758879,41675219715,122080952361,357926363463,1050260357829,3084183651309,9063723857271,26655094384653,78441446368179
%N a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 2, 3] as of [2, 3, 1].
%H Alois P. Heinz, <a href="/A211301/b211301.txt">Table of n, a(n) for n = 0..1000</a>
%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
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