This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A340813 #11 Mar 13 2021 16:26:04 %S A340813 1,1,1,3,11,49,252,1406,8405,52348,337029,2225333,15002763,102896407, %T A340813 716106077,5046649182,35956186581,258649116963,1876462272125, %U A340813 13717081730294,100957850485311,747631534534529,5567459642741752,41671027665802639,313351688709886964,2366390596263188755 %N A340813 Number of oriented polygonal 2-trees with n oriented quadrilaterals. %H A340813 Andrew Howroyd, <a href="/A340813/b340813.txt">Table of n, a(n) for n = 0..200</a> %H A340813 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 A340813 (PARI) C(25,4) \\ See A340812 for C(n,k). %Y A340813 Column k=4 of A340812. %K A340813 nonn %O A340813 0,4 %A A340813 _Andrew Howroyd_, Feb 02 2021