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Search: id:A146303
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| A146303 |
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Number of distinct ways to place queens (even fewer than n) on a n*n chessboard so that no queen is attacking another and that it is not possible to add another queen. |
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+0
2
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| 1, 4, 9, 18, 58, 348, 1862, 10188, 57600, 376692, 2640422
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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S. W. Golomb and L. D. Baumert, Backtrack Programming, Journal of the ACM, 4 (2001), 516-524.
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EXAMPLE
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For n=2, the a(n) = 4 solutions are to place a single queen in each of the squares of the chessboard. For n=3, there is a single one-queen solution (placing the queen in b2) and eight two-queen solutions, but no three-queen solution (see A000170).
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CROSSREFS
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Cf. A000170, A146304
Sequence in context: A074896 A015713 A049198 this_sequence A147977 A045278 A075649
Adjacent sequences: A146300 A146301 A146302 this_sequence A146304 A146305 A146306
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KEYWORD
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hard,nonn
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AUTHOR
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Paolo Bonzini (bonzini(AT)gnu.org), Oct 29 2008
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