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A172222 Number of ways to place 4 nonattacking zebras on a 4 X n board. 3
1, 70, 406, 1168, 2948, 6576, 13122, 23808, 40168, 63996, 97344, 142516, 202072, 278828, 375856, 496484, 644296, 823132, 1037088, 1290516, 1588024, 1934476, 2334992, 2794948, 3319976 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Zebra is a (fairy chess) leaper [2,3].

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

Eric Weisstein's World of Mathematics, Zebra Graph

Wikipedia, Zebra (chess)

FORMULA

a(n) = 4*(8*n^4 - 48*n^3 + 202*n^2 - 471*n + 507)/3, n>=9.

G.f.: -x * (4*x^12 -6*x^11 -2*x^10 -52*x^9 +160*x^8 -88*x^7 +2*x^6 -195*x^5 +473*x^4 -172*x^3 +66*x^2 +65*x +1) / (x-1)^5. - Vaclav Kotesovec, Mar 25 2010

MATHEMATICA

CoefficientList[Series[-(4 x^12 - 6 x^11 - 2 x^10 - 52 x^9 + 160 x^8 - 88 x^7 + 2 x^6 - 195 x^5 + 473 x^4 - 172 x^3 + 66 x^2 + 65 x + 1) / (x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, May 28 2013 *)

CROSSREFS

Cf. A172139, A061990, A172221.

Sequence in context: A174534 A295770 A151556 * A157369 A163434 A154085

Adjacent sequences:  A172219 A172220 A172221 * A172223 A172224 A172225

KEYWORD

nonn,easy

AUTHOR

Vaclav Kotesovec, Jan 29 2010

STATUS

approved

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