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 A129524 #9 Nov 08 2019 15:58:46 %S A129524 0,0,1,6,79,1499,35317,967255,29949217,1033242585,39323062014, %T A129524 1637375262965,74075329383599,3619112881630497,189953824713590782, %U A129524 10661151595417930874,637230479685691806302,40415532825383300892418,2711124591869919503655096 %N A129524 Number of unlabeled digraphs on n vertices such that every vertex has outdegree 2. %H A129524 Andrew Howroyd, <a href="/A129524/b129524.txt">Table of n, a(n) for n = 1..50</a> %H A129524 L. Travis, <a href="http://arXiv.org/abs/math.CO/9811127">[math/9811127] Graphical Enumeration: A Species-Theoretic Approach</a> %Y A129524 Column k=2 of A329228. %Y A129524 Cf. A001373, A185193, A185194, A185303. %K A129524 nonn %O A129524 1,4 %A A129524 _Vladeta Jovovic_, May 29 2007 %E A129524 Terms a(10) and beyond from _Andrew Howroyd_, Nov 08 2019