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 A020559 #25 Apr 24 2019 06:12:20
%S A020559 1,2,11,97,1219,20385,433022,11296844,352866598,12938878499,
%T A020559 548257129281,26503637228615,1446212232918009,88278080019931590,
%U A020559 5981590442549971867,446907535344317788261,36602523445840041088223
%N A020559 Number of ordered multigraphs on n labeled edges (with loops).
%D A020559 G. Paquin, Dénombrement de multigraphes enrichis, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004.
%H A020559 G. Labelle, <a href="https://doi.org/10.1016/S0012-365X(99)00265-4">Counting enriched multigraphs according to the number of their edges (or arcs)</a>, Discrete Math., 217 (2000), 237-248.
%H A020559 G. Paquin, <a href="/A038205/a038205.pdf">Dénombrement de multigraphes enrichis</a>, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004. [Cached copy, with permission]
%F A020559 E.g.f.: exp((3*x-2)/(2-2*x))*Sum_{n>=0}1/(n!*(1-x)^binomial(n+1, 2)). - _Vladeta Jovovic_, May 02 2004
%F A020559 a(n) = Sum_{k=0..n} (-1)^(n-k) * Stirling1(n, k) * A020555(k). - _Sean A. Irvine_, Apr 24 2019
%Y A020559 Cf. A020555, A020558.
%K A020559 nonn
%O A020559 0,2
%A A020559 Gilbert Labelle (gilbert(AT)lacim.uqam.ca), _Simon Plouffe_