

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


LINKS

Table of n, a(n) for n=1..30.
N. Johnston, On Maximal SelfAvoiding Walks.


CROSSREFS

Cf. A046994, A046995, A145156, A145157.
Sequence in context: A167498 A250388 A231248 * A069669 A145359 A306096
Adjacent sequences: A160237 A160238 A160239 * A160241 A160242 A160243


KEYWORD

nonn


AUTHOR

Nathaniel Johnston, May 05 2009


EXTENSIONS

a(11)a(30) from Andrew Howroyd, Nov 07 2015


STATUS

approved



