

A169773


Number of open knight's tour diagrams of a 3 X n chessboard that are symmetric under 180degree rotation and have "type X": both endpoints occur in the same column.


2



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, 0, 0, 2087344, 0, 0, 0, 20207664, 0, 0, 0, 197082624, 0, 0, 0, 1916054112, 0, 0, 0, 18652927040, 0, 0, 0, 181485750208, 0, 0, 0, 1766199186560, 0, 0, 0
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OFFSET

4,6


REFERENCES

D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010.


LINKS

Table of n, a(n) for n=4..60.
George Jelliss, Open knight's tours of threerank boards, Knight's Tour Notes, note 3a (21 October 2000).
George Jelliss, Closed knight's tours of threerank boards, Knight's Tour Notes, note 3b (21 October 2000).
D. E. Knuth Generating functions for A169770A169777 and A169696.


FORMULA

A169773(n)=0 unless n mod 4 = 1.


CROSSREFS

Cf. A070030, A169696, A169764A169777.
Sequence in context: A284117 A183099 A162296 * A236380 A298825 A265831
Adjacent sequences: A169770 A169771 A169772 * A169774 A169775 A169776


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, May 10 2010, based on a communication from Don Knuth, Apr 28 2010


EXTENSIONS

a(31)a(60) from Andrew Howroyd, Jul 01 2017


STATUS

approved



