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Search: id:A061995
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| A061995 |
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Number of ways to place 2 nonattacking kings on an n X n board. |
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+0
4
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| 0, 0, 0, 16, 78, 228, 520, 1020, 1806, 2968, 4608, 6840, 9790, 13596, 18408, 24388, 31710, 40560, 51136, 63648, 78318, 95380, 115080, 137676, 163438, 192648, 225600, 262600, 303966, 350028, 401128, 457620, 519870, 588256
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OFFSET
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0,4
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LINKS
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Vaclav Kotesovec, Number of ways of placing non-attacking queens and kings on boards of various sizes, part of V. Kotesovec, Between chessboard and computer, 1996, pp. 204 - 206.
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FORMULA
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G.f.: 2*x^3*( - 8 + x + x^2)/(x - 1)^5; Recurrence: a(n) = 5*a(n - 1) - 10*a(n - 2) + 10*a(n - 3) - 5*a(n - 4) + a(n - 5), n >= 6. Explicit formula: a(n) = (n - 1)*(n - 2)*(n^2 + 3*n - 2)/2, n >= 1.
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CROSSREFS
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Cf. A061996, A061997, A061998.
Sequence in context: A118532 A007834 A082966 this_sequence A044203 A044584 A111732
Adjacent sequences: A061992 A061993 A061994 this_sequence A061996 A061997 A061998
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KEYWORD
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nonn
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AUTHOR
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Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), May 31 2001
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