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A051755
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Consider problem of placing N queens on an n X n board so that each queen attacks precisely 2 others. Sequence gives maximal number of queens.
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4
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3, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130
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OFFSET
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2,1
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REFERENCES
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Peter Hayes, A Problem of Chess Queens, Journal of Recreational Mathematics, 24(4), 1992, 264-271.
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LINKS
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Table of n, a(n) for n=2..66.
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FORMULA
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a(2)=3, a(n)=2n-2 for n >= 3.
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MATHEMATICA
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CoefficientList[Series[(z^2 - 2*z + 3)/(z - 1)^2, {z, 0, 100}], z] (* and *) Join[{3}, Table[2*n, {n, 2, 200}]] (* From Vladimir Joseph Stephan Orlovsky, Jul 10 2011 *)
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CROSSREFS
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Cf. A051754-A051759, A051567-A051571, A019654.
Sequence in context: A184736 A173472 A058992 * A092535 A215476 A204662
Adjacent sequences: A051752 A051753 A051754 * A051756 A051757 A051758
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KEYWORD
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nonn,nice
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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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More terms from Jud McCranie, Aug 11 2001
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STATUS
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approved
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