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A160240 Number of Greek-Key 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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Greek Key Tours are self-avoiding walks that touch every vertex of the grid and start at the bottom-left 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
CROSSREFS
Sequence in context: A167498 A250388 A231248 * A069669 A145359 A306096
KEYWORD
nonn
AUTHOR
Nathaniel Johnston, May 05 2009
EXTENSIONS
a(11)-a(30) from Andrew Howroyd, Nov 07 2015
STATUS
approved

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Last modified July 20 22:04 EDT 2024. Contains 374461 sequences. (Running on oeis4.)