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 A054957 #19 Apr 14 2017 17:57:27 %S A054957 1,1,6,118,7000,1329496,868255024,2039295163312,17639804273910144, %T A054957 569596637165777524096,69273803156588266525129984, %U A054957 31940576331984155835757999795456,56121305700570450429977355284230355968,377361653292638108206937443603065676106341376 %N A054957 Number of labeled connected Eulerian digraphs with n nodes. %H A054957 Alois P. Heinz, <a href="/A054957/b054957.txt">Table of n, a(n) for n = 1..16</a> %H A054957 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 A054957 a(n) = A054958(n) + A054959(n). - _R. J. Mathar_, Apr 13 2017 %Y A054957 Cf. A058338, A054955, A007080 (EXP-transform), A054959, A054956, A058337, A054958. %K A054957 nonn,easy %O A054957 1,3 %A A054957 _N. J. A. Sloane_, May 24 2000 %E A054957 More terms from _Vladeta Jovovic_, Mar 06 2001 %E A054957 More terms from _Alois P. Heinz_, Apr 14 2017