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 A364651 #20 Jun 12 2025 21:38:10 %S A364651 0,0,0,20,206,1282,6302,26942,104948,382444,1325444,4417024,14263474, %T A364651 44884286,138222194,417923290,1243857480,3651728760,10592838440, %U A364651 30403009612,86440264694,243689593114,681776739174,1894276352726,5230101132028,14357448589988 %N A364651 Number of 6-cycles in the n-Pell graph. %H A364651 Andrew Howroyd, <a href="/A364651/b364651.txt">Table of n, a(n) for n = 0..1000</a> %H A364651 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GraphCycle.html">Graph Cycle</a>. %H A364651 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PellGraph.html">Pell Graph</a>. %H A364651 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (8,-20,8,26,-8,-20,-8,-1). %F A364651 From _Andrew Howroyd_, Jun 12 2025: (Start) %F A364651 G.f.: 16*x^3*(1 + x)^3/(1 - 2*x - x^2)^4 + 2*x^3*(1 + x)*(2 + x)/(1 - 2*x - x^2)^3. %F A364651 G.f.: 2*x^3*(10 + 23*x + 17*x^2 + 3*x^3 - x^4)/(1 - 2*x - x^2)^4. (End) %o A364651 (PARI) seq(n) = Vec(2*x^3*(10 + 23*x + 17*x^2 + 3*x^3 - x^4)/(1 - 2*x - x^2)^4 + O(x*x^n), -n-1) \\ _Andrew Howroyd_, Jun 12 2025 %Y A364651 Cf. A290031, A364619 (number of 4-cycles). %K A364651 nonn,easy %O A364651 0,4 %A A364651 _Eric W. Weisstein_, Jul 31 2023 %E A364651 a(10)-a(12) from _Eric W. Weisstein_, Dec 07 2023 %E A364651 a(13) onwards from _Andrew Howroyd_, Jun 12 2025