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A179060
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Number of non-attacking placements of 5 rooks on an n X n board.
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4
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0, 0, 0, 0, 120, 4320, 52920, 376320, 1905120, 7620480, 25613280, 75271680, 198764280, 480960480, 1082161080, 2289530880, 4594961280, 8809274880, 16225246080, 28844881920, 49689816120, 83217546720, 135870624120
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OFFSET
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1,5
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).
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FORMULA
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a(n) = 5! * binomial(n, 5)^2.
G.f.: -120*x^5*(x+1)*(x^4+24*x^3+76*x^2+24*x+1) / (x-1)^11. - Colin Barker, Jan 08 2013
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MATHEMATICA
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a[n_] := If[n<5, 0, Coefficient[n!*LaguerreL[n, x], x, n-5] // Abs];
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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