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 A054933 #24 Aug 29 2019 09:57:03
%S A054933 1,3,13,144,5158,778084,441288796,896699384640,6513980949408584,
%T A054933 170630216624502796000,16261454692830032538976880,
%U A054933 5683372715412978313604073582912,7334542846356465411966209047539403296,35157828307617499762304829312302735958971072,629172630775224433640531447950565255471723325434560
%N A054933 Number of unlabeled digraphs on n nodes up to reversing the arcs.
%H A054933 Andrew Howroyd, <a href="/A054933/b054933.txt">Table of n, a(n) for n = 1..50</a>
%H A054933 A. Gainer-Dewar, <a href="http://arxiv.org/abs/1401.6202">Pólya theory for species with an equivariant group action</a>, arXiv:1401.6202 [math.CO], 2014. Also Andrew Gainer-Dewar, Species with an equivariant group action, AUSTRALASIAN JOURNAL OF COMBINATORICS, Volume 63(2) (2015), Pages 202-225.
%H A054933 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 A054933 a(n) = (A000273(n) + A002499(n))/2.
%t A054933 A000273 = Cases[Import["https://oeis.org/A000273/b000273.txt", "Table"], {_, _}][[All, 2]];
%t A054933 A002499 = Cases[Import["https://oeis.org/A002499/b002499.txt", "Table"], {_, _}][[All, 2]];
%t A054933 a[n_] := (A000273[[n + 1]] + A002499[[n]])/2;
%t A054933 Array[a, 50] (* _Jean-François Alcover_, Aug 29 2019 *)
%Y A054933 Cf. A000273, A002499.
%K A054933 nonn,easy
%O A054933 1,2
%A A054933 _N. J. A. Sloane_, May 24 2000