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A211294 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 [2, 2, 1]. 1

%I

%S 1,3,9,25,69,193,543,1533,4341,12331,35131,100369,287511,825643,

%T 2376563,6855891,19818729,57402023,166556929,484093953,1409218111,

%U 4108293369,11993207211,35055708423,102587243163,300540887595,881366127909,2587147501819,7600984533115,22349936569297,65768286284401

%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 [2, 2, 1].

%H Alois P. Heinz, <a href="/A211294/b211294.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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Last modified January 28 12:07 EST 2022. Contains 350656 sequences. (Running on oeis4.)