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A051759
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Consider the problem of placing A051756(n) queens on an n X n board so that each queen attacks precisely 3 others. Sequence gives number of solutions up to square symmetry.
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13
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OFFSET
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2,2
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COMMENTS
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A051569 (taken from the Martin Gardner references) is another version of this sequence. - N. J. A. Sloane, May 22 2014
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REFERENCES
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M. Gardner, The Last Recreations, Springer, 1997, p. 282.
M. Gardner, The Colossal Book of Mathematics, 2001, p. 209.
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LINKS
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CROSSREFS
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KEYWORD
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nonn,nice,more
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AUTHOR
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Robert Trent (trentrd(AT)hotmail.com), Aug 23 2000
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EXTENSIONS
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STATUS
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approved
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