%I #23 Sep 10 2023 21:04:47
%S 3,30,198,1326,8886,59550,399078,2674446,17922966,120111870,804937158,
%T 5394336366,36150480246,242264688990,1623551862438,10880333659086,
%U 72915231888726,488645955902910,3274691227542918,21945546680994606,147069444311876406,985595016821145630
%N Number of Hamiltonian cycles in K_4 X P_n.
%H Frans J. Faase, <a href="http://www.iwriteiam.nl/Cpaper.zip">On the number of specific spanning subgraphs of the graphs G X P_n</a>, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
%H Frans J. Faase, <a href="http://www.iwriteiam.nl/counting.html">Counting Hamiltonian cycles in product graphs</a>
%H Frans J. Faase, <a href="http://www.iwriteiam.nl/Cresults.html">Results from the counting program</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7,-2).
%F a(n) = 7*a(n-1) - 2*a(n-2), n>3.
%F G.f.: 3*x*(1+3*x-2*x^2)/(1-7*x+2*x^2). - _R. J. Mathar_, Dec 16 2008
%K nonn,easy
%O 1,1
%A _Frans J. Faase_
%E More terms from _Stefano Spezia_, May 13 2023