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A172208 Number of ways to place 4 nonattacking bishops on a 4 X n board. 3
1, 9, 61, 260, 927, 2578, 5965, 12066, 22135, 37678, 60457, 92488, 136043, 193650, 268093, 362412, 479903, 624118, 798865, 1008208, 1256467, 1548218, 1888293, 2281780, 2734023, 3250622, 3837433, 4500568, 5246395, 6081538, 7012877 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

V. Kotesovec, Number of ways of placing non-attacking queens and kings on boards of various sizes

FORMULA

a(n) = (32*n^4 -336*n^3 +1702*n^2 -4701*n +5844) / 3, n>=9.

G.f.: -x * (2*x^12 -2*x^11 +4*x^10 -24*x^9 +50*x^8 -10*x^7 +41*x^6 -23*x^5 +152*x^4 +35*x^3 +26*x^2 +4*x+1) / (x-1)^5. - Vaclav Kotesovec, Mar 25 2010

MATHEMATICA

CoefficientList[Series[-1 (2 x^12 - 2 x^11 + 4 x^10 - 24 x^9 + 50 x^8 - 10 x^7 + 41 x^6 - 23 x^5 + 152 * x^4 + 35 x^3 + 26  x^2 + 4 x + 1) / (x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, May 27 2013 *)

CROSSREFS

Cf. A172127, A061990, A172207.

Sequence in context: A138589 A058777 A030507 * A202660 A202120 A201084

Adjacent sequences:  A172205 A172206 A172207 * A172209 A172210 A172211

KEYWORD

nonn,easy

AUTHOR

Vaclav Kotesovec, Jan 29 2010

STATUS

approved

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Last modified December 18 20:06 EST 2018. Contains 318245 sequences. (Running on oeis4.)