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 A368190 #19 Feb 16 2025 08:34:06
%S A368190 0,1,11,249,74835,5890739121,34755832523270764251,
%T A368190 1207969003612007237832573159205646499369,
%U A368190 1459189113687796591938380205390010178829792070192521048490799792728844237848995
%N A368190 Number of (undirected) cycles in the n-Dorogovtsev-Goltsev-Mendes graph.
%C A368190 Using the indexing convention that DGM(0) = P_2.
%C A368190 For n > 0, DGM(n) contains a unique longest cycle of length 3*2^(n-1).
%H A368190 Andrew Howroyd, <a href="/A368190/b368190.txt">Table of n, a(n) for n = 0..11</a>
%H A368190 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Dorogovtsev-Goltsev-MendesGraph.html">Dorogovtsev-Goltsev-Mendes Graph</a>.
%H A368190 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GraphCycle.html">Graph Cycle</a>.
%F A368190 a(n) = 3*a(n-1) + A007018(n-1)^3 for n > 0. - _Andrew Howroyd_, Dec 30 2023
%o A368190 (PARI) a(n) = {my(t=0,b=1); for(k=1, n, t = 3*t + b^3; b += b^2); t} \\ _Andrew Howroyd_, Dec 30 2023
%Y A368190 Cf. A007018, A368456, A367967 (5-cycles), A367968 (6-cycles).
%K A368190 nonn
%O A368190 0,3
%A A368190 _Eric W. Weisstein_, Dec 16 2023
%E A368190 Offset corrected and a(5) from _Eric W. Weisstein_, Dec 29 2023
%E A368190 Terms a(6) and beyond from _Andrew Howroyd_, Dec 30 2023