%I #17 Dec 20 2016 09:42:57

%S 1,6,32,5660,4924128,45707720232,3244086234829248,

%T 1923484178952564643368

%N Number of directed "king tours" on an n X n board.

%C Or, number of directed Hamiltonian cycles in the graph P_n X P_n.

%C If the direction of the tour is not taken into account, the numbers for n > 1 must be halved (see A140519).

%C Computed using ZDDs (ZDD = "reduced, order, zero-suppressed binary decision diagram").

%D Donald E. Knuth, The Art of Computer Programming, Vol. 4, fascicle 1, section 7.1.4, p. 117, Addison-Wesley, 2009.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HamiltonianCycle.html">Hamiltonian Cycle</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/KingGraph.html">King Graph</a>

%H <a href="/index/Gra#graphs">Index entries for sequences related to graphs, Hamiltonian</a>

%Y Cf. A001230, A140519.

%K nonn,walk

%O 1,2

%A _Don Knuth_, Jul 26 2008