A179060 - OEIS

A179060

Number of non-attacking placements of 5 rooks on an n X n board.

0, 0, 0, 0, 120, 4320, 52920, 376320, 1905120, 7620480, 25613280, 75271680, 198764280, 480960480, 1082161080, 2289530880, 4594961280, 8809274880, 16225246080, 28844881920, 49689816120, 83217546720, 135870624120

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,5

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..200

Christopher R. H. Hanusa, T. Zaslavsky, and S. Chaiken, A q-Queens Problem. IV. Queens, Bishops, Nightriders (and Rooks), arXiv preprint arXiv:1609.00853 [math.CO], 2016-2020.

Index entries for linear recurrences with constant coefficients, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).

FORMULA

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

MATHEMATICA

a[n_] := If[n<5, 0, Coefficient[n!*LaguerreL[n, x], x, n-5] // Abs];

Array[a, 30] (* Jean-François Alcover, Jun 14 2018, after A144084 *)

PROG

(PARI) a(n) = 5! * binomial(n, 5)^2 \\ Andrew Howroyd, Feb 13 2018

CROSSREFS

Column k=5 of A144084.

Cf. A179059 (4 rooks), A179061 (6 rooks).