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%I #10 Sep 10 2020 19:29:08
%S 1,3,9,25,70,200,569,1614,4596,13114,37431,106978,306238,877713,
%T 2518647,7236947,20820856,59975554,172974739,499480558,1444006498,
%U 4179496707,12110820951,35132286213,102025868324,296601381043,863142552053,2514348427139,7331433782002,21397338280852,62506435095245
%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, 1] as of [1, 2, 1].
%H Alois P. Heinz, <a href="/A211283/b211283.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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