

A137279


Number of ways of placing ceiling(n/2) nonattacking queens on an n X n Mobius chessboard.


0



1, 4, 0, 16, 40, 192, 560, 3328, 11772, 63840, 259336, 1550976, 7169656, 42410256, 234044160, 1366190592
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OFFSET

1,2


COMMENTS

The chessboard is an n X n standard chessboard whose left and right edges are twisted connected.


LINKS

Table of n, a(n) for n=1..16.
J. Bell and B. Stevens, Results for the nqueens problem on the Mobius board, Australasian Journal of Combinatorics, vol.42, p.21 (2008).


EXAMPLE

a(4)=16 because any queen attacks all but two other squares and every solution is counted twice by enumerating all such placements.


CROSSREFS

Cf. A000170, A007705, A002562, A053994, A061989, A061990.
Sequence in context: A057378 A247120 A002979 * A233807 A302771 A167350
Adjacent sequences: A137276 A137277 A137278 * A137280 A137281 A137282


KEYWORD

nonn,more


AUTHOR

Brett Stevens (brett(AT)math.carleton.ca), Mar 13 2008


STATUS

approved



