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%I #19 Dec 23 2023 13:49:00
%S 3,54,1140,24360,521064,11146656,238452456,5101047216,109123156248,
%T 2334395822496,49938107061384,1068291209653392,22853211220567416,
%U 488882861126970624
%N Number of 2-factors in P_5 X P_2n.
%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>
%F a(n) = 24a(n-1) - 57a(n-2) + 26a(n-3), n>3.
%F G.f.: 3x(1-5x)(1-x)/((1-2x)(1-22x+13x^2)). [From _R. J. Mathar_, Dec 16 2008]
%K nonn
%O 1,1
%A _Frans J. Faase_
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