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 A219890 #14 Feb 06 2022 15:01:05 %S A219890 1,2,23,415,19041,1104045,79818336,6958257941,720814138673, %T A219890 87579097910309 %N A219890 Number of directed 3-regular graphs on n nodes. %H A219890 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 A219890 Column k=3 of A350910. %Y A219890 Cf. A096368, A219889, A219890, A219891, A219892, A219893. %K A219890 nonn,more %O A219890 4,2 %A A219890 _N. J. A. Sloane_, Nov 30 2012