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A051906 Number of ways of placing n nonattacking toroidal queens on an n X n chessboard. 6
1, 0, 0, 0, 10, 0, 28, 0, 0, 0, 88, 0, 4524, 0, 0, 0, 140692, 0, 820496, 0, 0, 0, 128850048, 0, 1957725000, 0, 0, 0, 605917055356, 0, 13404947681712, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

The sequence is given to n=23 in the reference. Further terms were calculated by the submitter, Dec 17 1999 and Jan 11 2001.

a(n) is divisible by n.

LINKS

Table of n, a(n) for n=1..34.

M. R. Engelhardt, A group-based search for solutions of the n-queens problem, Discr. Math., 307 (2007), 2535-2551.

V. Kotesovec, Non-attacking chess pieces, 6ed, 2013

Kevin Pratt, Closed-Form Expressions for the n-Queens Problem and Related Problems, arXiv:1609.09585 [cs.DM], 2016.

I. Rivin, I. Vardi and P. Zimmermann, The n-queens problem, Amer. Math. Monthly, 101 (1994), 629-639.

CROSSREFS

See A007705, which is the main entry for this sequence.

Sequence in context: A107781 A107772 A087474 * A171809 A167302 A214122

Adjacent sequences:  A051903 A051904 A051905 * A051907 A051908 A051909

KEYWORD

nonn,nice,hard,more

AUTHOR

Matthias Engelhardt, Dec 17 1999

EXTENSIONS

Term a(31) added from A007705 by Vaclav Kotesovec, Aug 25 2012

STATUS

approved

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Last modified June 23 15:27 EDT 2017. Contains 288666 sequences.