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 A054955 #18 Aug 27 2019 10:11:31
%S A054955 1,2,8,88,3928,688336,438953344,1023160206720,8829110851362176,
%T A054955 284886609918484446976,34640035331694391965082624,
%U A054955 15970703846423879100652101753856,28060860469435555251136195653129640960,188681219498365676664628141013181402003089408
%N A054955 Number of labeled Eulerian digraphs with n nodes and an even number of edges.
%H A054955 V. A. Liskovets, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/LISK/Derseq.html">Some easily derivable sequences</a>, J. Integer Sequences, 3 (2000), #00.2.2.
%F A054955 a(n) = (A007080(n) + n!)/2. - _Andrew Howroyd_, Sep 10 2018
%t A054955 A007080 = Cases[Import["https://oeis.org/A007080/b007080.txt", "Table"], {_, _}][[All, 2]];
%t A054955 a[n_] := (A007080[[n]] + n!)/2;
%t A054955 Array[a, 14] (* _Jean-François Alcover_, Aug 27 2019 *)
%Y A054955 Cf. A007080, A054956.
%K A054955 nonn,easy
%O A054955 1,2
%A A054955 _N. J. A. Sloane_, May 24 2000
%E A054955 More terms from _Vladeta Jovovic_, Mar 05 2001
%E A054955 a(12)-a(14) from _Andrew Howroyd_, Sep 10 2018