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 A308128 #15 Apr 12 2020 15:45:01 %S A308128 1,2,3,14,112,2174,124501,22400498,13010949171,24926846389076, %T A308128 160810397320789069,3554744065897655673978, %U A308128 273140190737719436311559660,73831786956788218320014098284918,70920392983384812245087697080226658475,244186402549448674084991238687021028510453186 %N A308128 Isomorphism classes of connected Eulerian digraphs with n vertices, allowing loops. %F A308128 Inverse Euler transform of A308111. %Y A308128 Cf. A058338, A229865, A308111. %K A308128 nonn,hard %O A308128 0,2 %A A308128 _Alois P. Heinz_, May 14 2019, following a suggestion from _Brendan McKay_ %E A308128 Terms a(10) and beyond from _Andrew Howroyd_, Apr 12 2020