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 A020560 #21 Apr 24 2019 05:32:51
%S A020560 1,1,8,110,2262,63822,2335856,106643980,5901564892,387251339836,
%T A020560 29612207398688,2601877956513640,259646660158526856,
%U A020560 29140784853464966632,3647614440065070983488,505553321559685235600720,77096697572750991426551056,12864789849511242132008021520
%N A020560 Number of ordered oriented multigraphs on n labeled arcs (without loops).
%H A020560 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 A020560 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 A020560 a(n) = Sum_{k=0..n} (-1)^(n-k) * Stirling1(n, k) * A020556(k). - _Sean A. Irvine_, Apr 24 2019
%Y A020560 Cf. A020556.
%K A020560 nonn
%O A020560 0,3
%A A020560 Gilbert Labelle (gilbert(AT)lacim.uqam.ca), _Simon Plouffe_