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%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