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A172203
Number of ways to place 4 nonattacking kings on a 4 X n board.
5
0, 0, 9, 79, 454, 1566, 4103, 9009, 17484, 30984, 51221, 80163, 120034, 173314, 242739, 331301, 442248, 579084, 745569, 945719, 1183806, 1464358, 1792159, 2172249, 2609924
OFFSET
1,3
FORMULA
a(n) = (64n^4 - 720n^3 + 3347n^2 - 7569n + 6894)/6, n>=3.
G.f.: -x^3*(68*x^4-4*x^3+149*x^2+34*x+9)/(x-1)^5. - Vaclav Kotesovec, Mar 24 2010
MATHEMATICA
CoefficientList[Series[- x^2 (68 x^4 - 4 x^3 + 149 x^2 + 34 x + 9) / (x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, May 27 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vaclav Kotesovec, Jan 29 2010
STATUS
approved