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%I #12 Jul 01 2017 22:59:21
%S 0,0,0,0,0,4,0,0,0,16,0,0,0,264,0,0,0,2144,0,0,0,22408,0,0,0,211808,0,
%T 0,0,2087344,0,0,0,20207664,0,0,0,197082624,0,0,0,1916054112,0,0,0,
%U 18652927040,0,0,0,181485750208,0,0,0,1766199186560,0,0,0
%N Number of open knight's tour diagrams of a 3 X n chessboard that are symmetric under 180-degree rotation and have "type X": both endpoints occur in the same column.
%D D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010.
%H George Jelliss, <a href="http://www.mayhematics.com/t/oa.htm">Open knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3a (21 October 2000).
%H George Jelliss, <a href="http://www.mayhematics.com/t/ob.htm">Closed knight's tours of three-rank boards</a>, Knight's Tour Notes, note 3b (21 October 2000).
%H D. E. Knuth <a href="/A169770/a169770.txt">Generating functions for A169770-A169777 and A169696.</a>
%F A169773(n)=0 unless n mod 4 = 1.
%Y Cf. A070030, A169696, A169764-A169777.
%K nonn
%O 4,6
%A _N. J. A. Sloane_, May 10 2010, based on a communication from _Don Knuth_, Apr 28 2010
%E a(31)-a(60) from _Andrew Howroyd_, Jul 01 2017
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