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%I #11 Mar 13 2021 16:26:04
%S 1,1,1,3,11,49,252,1406,8405,52348,337029,2225333,15002763,102896407,
%T 716106077,5046649182,35956186581,258649116963,1876462272125,
%U 13717081730294,100957850485311,747631534534529,5567459642741752,41671027665802639,313351688709886964,2366390596263188755
%N Number of oriented polygonal 2-trees with n oriented quadrilaterals.
%H Andrew Howroyd, <a href="/A340813/b340813.txt">Table of n, a(n) for n = 0..200</a>
%H G. Labelle, C. Lamathe and P. Leroux, <a href="http://arXiv.org/abs/math.CO/0312424">Labeled and unlabeled enumeration of k-gonal 2-trees</a>, arXiv:math/0312424 [math.CO], Dec 23 2003.
%o (PARI) C(25,4) \\ See A340812 for C(n,k).
%Y Column k=4 of A340812.
%K nonn
%O 0,4
%A _Andrew Howroyd_, Feb 02 2021