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%I #16 Jan 01 2019 06:31:05
%S 0,3,7,46,193,963,4470,21367,100909,478924,2268405,10753173,50957032,
%T 241508575,1144553203,5424374574,25707458901,121834519567,
%U 577405414054,2736475971043,12968875078785,61462896633780
%N Number of 2-factors in D_4 X P_n.
%D F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.
%H F. 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 F. Faase, <a href="http://www.iwriteiam.nl/counting.html">Counting Hamiltonian cycles in product graphs</a>
%H F. Faase, <a href="http://www.iwriteiam.nl/Cresults.html">Results from the counting program</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3, 9, -3, -3, 1).
%F a(n) = 3a(n-1) + 9a(n-2) - 3a(n-3) - 3a(n-4) + a(n-5), n>5.
%F G.f.: x^2*(1-x)(-x^2+x+3)/(1-3x-9x^2+3x^3+3x^4-x^5). [From _R. J. Mathar_, Dec 16 2008]
%K nonn
%O 1,2
%A _Frans J. Faase_
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