

A145157


Number of Greekkey tours on an n X n board; i.e., selfavoiding walks on n X n grid starting in top left corner.


6



1, 2, 8, 52, 824, 22144, 1510446, 180160012, 54986690944, 29805993260994, 41433610713353366, 103271401574007978038, 660340630211753942588170, 7618229614763015717175450784, 225419381425094248494363948728158
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OFFSET

1,2


COMMENTS

The sequence may be enumerated using standard methods for counting Hamilton 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 08 2015


LINKS

Table of n, a(n) for n=1..15.
N. Johnston, On Maximal SelfAvoiding Walks
Ville H. Pettersson, Enumerating Hamiltonian Cycles, The Electronic Journal of Combinatorics, Volume 21, Issue 4, 2014.


CROSSREFS

Cf. A046994, A046995, A145156, A160240, A160241.
Cf. A000532, A001184, A120443, A003763, A271507, A007764.
Sequence in context: A057629 A191507 A191602 * A183945 A193651 A195979
Adjacent sequences: A145154 A145155 A145156 * A145158 A145159 A145160


KEYWORD

hard,nonn,walk


AUTHOR

Nathaniel Johnston, Oct 03 2008


EXTENSIONS

a(9)a(15) from Andrew Howroyd, Nov 08 2015


STATUS

approved



