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%I #12 Jan 01 2019 06:31:05
%S 1,6,78,469,3501,22144,144476,899432,5585508,34092855,206571444,
%T 1241016042,7407467656,43975776229,259779839242,1528563721468,
%U 8960651209082,52368047294410,305173796833144,1774059940879290,10289839706255591,59564855651625602,344177608427972004,1985502681113986836,11437008315770485918,65791536638478271291,377999748832914166324,2169320756101096085597,12436728915873118081588,71232070407411735554025
%N Number of Greek-Key Tours on a 6 X n grid.
%C Greek Key Tours are self-avoiding walks that touch every vertex of the grid and start at the bottom-left corner.
%C 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
%H N. Johnston, <a href="http://www.nathanieljohnston.com/index.php/2009/05/on-maximal-self-avoiding-walks/">On Maximal Self-Avoiding Walks</a>.
%Y Cf. A046994, A046995, A145156, A145157.
%K nonn
%O 1,2
%A _Nathaniel Johnston_, May 05 2009
%E a(11)-a(30) from _Andrew Howroyd_, Nov 07 2015
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