

A160240


Number of GreekKey Tours on a 6 X n grid.


1



1, 6, 78, 469, 3501, 22144, 144476, 899432, 5585508, 34092855, 206571444, 1241016042, 7407467656, 43975776229, 259779839242, 1528563721468, 8960651209082, 52368047294410, 305173796833144, 1774059940879290, 10289839706255591, 59564855651625602, 344177608427972004, 1985502681113986836, 11437008315770485918, 65791536638478271291, 377999748832914166324, 2169320756101096085597, 12436728915873118081588, 71232070407411735554025
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OFFSET

1,2


COMMENTS

Greek Key Tours are selfavoiding walks that touch every vertex of the grid and start at the bottomleft corner.
The sequence may be enumerated using standard methods for counting Hamiltonian cycles on a modified graph with two additional nodes, one joined to a corner vertex and the other joined to all other vertices.  Andrew Howroyd, Nov 07 2015


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CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



