%I
%S 1,2,8,52,824,22144,1510446,180160012,54986690944,29805993260994,
%T 41433610713353366,103271401574007978038,660340630211753942588170,
%U 7618229614763015717175450784,225419381425094248494363948728158
%N Number of Greekkey tours on an n X n board; i.e., selfavoiding walks on n X n grid starting in top 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 08 2015
%H Nathaniel Johnston, <a href="http://www.njohnston.ca/2009/05/onmaximalselfavoidingwalks">On Maximal SelfAvoiding Walks</a>
%H Ville H. Pettersson, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v21i4p7">Enumerating Hamiltonian Cycles</a>, The Electronic Journal of Combinatorics, Volume 21, Issue 4, 2014.
%Y Cf. A046994, A046995, A145156, A160240, A160241.
%Y Cf. A000532, A001184, A120443, A003763, A271507, A007764.
%K hard,nonn,walk
%O 1,2
%A _Nathaniel Johnston_, Oct 03 2008
%E a(9)a(15) from _Andrew Howroyd_, Nov 08 2015
