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 A306447 #31 Feb 16 2025 08:33:55
%S A306447 3,9,16,29,56,110,225,469,991,2110,4511,9666,20736,44511,95575,205253,
%T A306447 440828,946817,2033628,4367986,9381949,20151433,43283195,92967882,
%U A306447 199685571,428904390,921243268,1978737467,4250128235,9128846273,19607840040,42115660645
%N A306447 Number of (undirected) Hamiltonian cycles in the n-antiprism graph.
%C A306447 Extended to a(1)-a(2) using the formula/recurrence.
%H A306447 Colin Barker, <a href="/A306447/b306447.txt">Table of n, a(n) for n = 1..1000</a>
%H A306447 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AntiprismGraph.html">Antiprism Graph</a>
%H A306447 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HamiltonianCycle.html">Hamiltonian Cycle</a>
%H A306447 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,-2,0,1).
%F A306447 a(n) = A124353(n)/2.
%F A306447 From _Colin Barker_, Jul 12 2020: (Start)
%F A306447 G.f.: x*(3 - 8*x^2 - 4*x^3 + 3*x^4) / ((1 - x)^2*(1 - x - 2*x^2 - x^3)).
%F A306447 a(n) = 3*a(n-1) - a(n-2) - 2*a(n-3) + a(n-5) for n>5.
%F A306447 (End)
%t A306447 LinearRecurrence[{3,-1,-2,0,1},{3,9,16,29,56},40] (* _Harvey P. Dale_, Aug 06 2020 *)
%o A306447 (PARI) Vec(x*(3 - 8*x^2 - 4*x^3 + 3*x^4) / ((1 - x)^2*(1 - x - 2*x^2 - x^3)) + O(x^35)) \\ _Colin Barker_, Jul 12 2020
%K A306447 nonn,easy
%O A306447 1,1
%A A306447 _Eric W. Weisstein_, May 04 2019