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 A219891 #10 Feb 06 2022 15:00:52 %S A219891 1,4,92,19041,6510087,2983458766,1775668832509,1349509467853512 %N A219891 Number of directed 4-regular graphs on n nodes. %H A219891 Gunnar Brinkmann, <a href="https://doi.org/10.1016/j.disc.2012.09.014">Generating regular directed graphs</a>, Discrete Math., 313 (2012), 1-7. %Y A219891 Column k=4 of A350910. %Y A219891 Cf. A096368, A219889, A219890, A219892, A219893. %K A219891 nonn,more %O A219891 5,2 %A A219891 _N. J. A. Sloane_, Nov 30 2012