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A006864 Number of Hamiltonian cycles in P_4 X P_n.
(Formerly M1603)
6
0, 1, 2, 6, 14, 37, 92, 236, 596, 1517, 3846, 9770, 24794, 62953, 159800, 405688, 1029864, 2614457, 6637066, 16849006, 42773094, 108584525, 275654292, 699780452, 1776473532, 4509783909, 11448608270, 29063617746, 73781357746, 187302518353, 475489124976 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Wazir tours on a 4 X n grid. There are two closed loops for a 4x4 board, appearing as an H and a C, for example. [Ed Pegg Jr, Sep 07 2010]

REFERENCES

F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154.

Kwong, Y. H. H.; Enumeration of Hamiltonian cycles in P_4 X P_n and P_5 X P_n. Ars Combin. 33 (1992), 87-96.

C. Flye Sainte-Marie, L'Intermediaire des Mathematiciens, vol. 11 (1904), pp. 86-88. [Ed Pegg Jr, Sep 07 2010]

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

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.

LINKS

Table of n, a(n) for n=1..31.

F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.

F. Faase, Counting Hamiltonian cycles in product graphs

F. Faase, Results from the counting program

George Jelliss, Wazir Wanderings [Ed Pegg Jr, Sep 07 2010]

FORMULA

a(n) = 2a(n-1) + 2a(n-2) - 2a(n-3) + a(n-4).

G.f.: x^2/(1-2x-2x^2+2x^3-x^4). - R. J. Mathar, Dec 16 2008

a(n)=sum ( sum ( binomial(k,j) * sum (binomial(j, i-j)*2^j *binomial(k-j,n-i-3*(k-j))*(-2)^(4*(k-j)-(n-i)), i,j,n-k+j) , j,0,k) , k,1,n ), n>0. - Vladimir Kruchinin, Aug 04 2010

PROG

(Maxima) a(n):=sum ( sum ( binomial(k, j) *sum (binomial(j, i-j)*2^j *binomial(k-j, n-i-3*(k-j))*(-2)^(4*(k-j)-(n-i)), i, j, n-k+j) , j, 0, k) , k, 1, n ); /* Vladimir Kruchinin, Aug 04 2010 */

CROSSREFS

Sequence in context: A144530 A248113 A026598 * A217420 A071636 A263758

Adjacent sequences:  A006861 A006862 A006863 * A006865 A006866 A006867

KEYWORD

easy,nonn

AUTHOR

kwong(AT)cs.fredonia.edu (Harris Kwong), N. J. A. Sloane, Simon Plouffe and Frans J. Faase

STATUS

approved

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Last modified February 22 09:34 EST 2019. Contains 320389 sequences. (Running on oeis4.)