%I A006864 M1603
%S A006864 0,1,2,6,14,37,92,236,596,1517,3846,9770,24794,62953,159800,405688,
%T A006864 1029864,2614457,6637066,16849006,42773094,108584525,275654292,
%U A006864 699780452,1776473532,4509783909,11448608270,29063617746
%N A006864 Number of Hamilton cycles in P_4 X P_n.
%D A006864 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A006864 F. Faase, On the number of specific spanning subgraphs of the graphs 
               G X P_n, Ars Combin. 49 (1998), 129-154.
%D A006864 Kwong, Y. H. H.; Enumeration of Hamiltonian cycles in $P\sb 4\times P\sb 
               n$ and $P\sb 5\times P\sb n$. Ars Combin. 33 (1992), 87-96.
%D A006864 Tosic R., Bodroza O., Harris Kwong Y. H. and Joseph Straight H., On the 
               number of Hamiltonian cycles of P4 X Pn, Indian J. Pure Appl. Math. 
               21 (5) (1990), 403-409.
%H A006864 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 A006864 F. Faase, <a href="http://www.iwriteiam.nl/counting.html">Counting Hamilton 
               cycles in product graphs</a>
%H A006864 F. Faase, <a href="http://www.iwriteiam.nl/Cresults.html">Results from 
               the counting program</a>
%H A006864 F. Faase, <a href="http://home.wxs.nl/~faase009/counting.html">Counting 
               Hamilton cycles in product graphs</a>
%F A006864 a(n) = 2a(n-1) + 2a(n-2) - 2a(n-3) + a(n-4).
%F A006864 G.f.: x^2/(1-2x-2x^2+2x^3-x^4). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Dec 16 2008]
%Y A006864 Sequence in context: A006653 A144530 A026598 this_sequence A071636 A100067 
               A026597
%Y A006864 Adjacent sequences: A006861 A006862 A006863 this_sequence A006865 A006866 
               A006867
%K A006864 easy,nonn
%O A006864 1,3
%A A006864 kwong(AT)cs.fredonia.edu (Harris Kwong), N. J. A. Sloane (njas(AT)research.att.com), 
               Simon Plouffe and Frans Faase (Frans_LiXia(AT)wxs.nl)