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 A061990 Number of ways to place 4 nonattacking queens on a 4 X n board. 15
 0, 0, 0, 0, 2, 12, 46, 140, 344, 732, 1400, 2468, 4080, 6404, 9632, 13980, 19688, 27020, 36264, 47732, 61760, 78708, 98960, 122924, 151032, 183740, 221528, 264900, 314384, 370532, 433920, 505148, 584840, 673644, 772232, 881300 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 V. Kotesovec, Ways of placing non-attacking queens and kings..., part of "Between chessboard and computer", 1996, pp. 204 - 206. E. Lucas, Recreations mathematiques I, Albert Blanchard, Paris, 1992, p. 231. Index entries for linear recurrences with constant coefficients, signature (5, -10, 10, -5, 1). FORMULA G.f.: -2*x^4*(x^3-x^2+x+1)*(x^4+4*x^2+1)/(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 >= 12. Explicit formula (H. Tarry, 1890): a(n)=n^4-18*n^3+139*n^2-534*n+840, n >= 7. MATHEMATICA Join[{0, 0, 0, 0, 2, 12, 46}, LinearRecurrence[{5, -10, 10, -5, 1}, {140, 344, 732, 1400, 2468}, 30]] (* Harvey P. Dale, Mar 06 2013 *) CoefficientList[Series[-2 x^4 (x^3 - x^2 + x + 1) (x^4 + 4 x^2 + 1) / (x-1)^5, {x, 0, 40}], x] (* Vincenzo Librandi, May 02 2013 *) CROSSREFS Cf. A061989. Sequence in context: A123771 A046991 A188982 * A006742 A003993 A129018 Adjacent sequences:  A061987 A061988 A061989 * A061991 A061992 A061993 KEYWORD nonn AUTHOR Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), May 29 2001 STATUS approved

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Last modified December 18 21:01 EST 2018. Contains 318245 sequences. (Running on oeis4.)