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 A004066 #23 Jul 30 2025 17:48:15 %S A004066 0,0,1,1,2,6,14,41,157,725,4196,29817,246646,2297088,23503564, %T A004066 260265650,3090341095,39101587595,524783295041,7443251159470, %U A004066 111222017297268,1746166043555813,28734210790531045,494526547845483641,8883866458982018870,166286444108288113541,3237719185652343485853,65477290060076644381373 %N A004066 Number of simple regular trivalent bicolored graphs with 2n nodes. %H A004066 Sean A. Irvine, <a href="/A004066/a004066.png">On the difference between A004066 and A008325</a> %H A004066 Patric R. J. Östergård, <a href="https://doi.org/10.1007/s10623-025-01694-w">Classifying generalized Howell designs</a>, Designs Codes Cryptog. (2025). See Sect. 3.2.1. %F A004066 a(n) = (A000840(n) + A000512(n))/2. - _Andrew Howroyd_, Apr 01 2020 %Y A004066 Cf. A000512, A000840, A008325 (bipartite), A006823 (connected). %K A004066 nonn %O A004066 1,5 %A A004066 _Gunnar Brinkmann_, _Brendan McKay_ and Eric Rogoyski %E A004066 a(1)-a(2) prepended and terms a(15) and beyond from _Andrew Howroyd_, Apr 01 2020