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 A172139 Number of ways to place 4 nonattacking zebras on an n X n board. 5
 0, 1, 126, 1168, 7334, 35749, 137970, 438984, 1208246, 2969389, 6662480, 13873100, 27144408, 50389581, 89424014, 152638280, 251834530, 403250693, 628798516, 957543164, 1427453780, 2087456085, 2999819778, 4242915176 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Zebra is a (fairy chess) leaper [2,3]. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA a(n) = (n^8 - 54n^6 + 240n^5 + 827n^4 - 8592n^3 + 10362n^2 + 75600n - 204864)/24, n >= 9. G.f.: x^2*(64*x^15-376*x^14+760*x^13-650*x^12+1478*x^11-6838*x^10+15166*x^9-17006*x^8+8858*x^7-462*x^6-2109*x^5+1333*x^4+1274*x^3+70*x^2+117*x+1)/(1-x)^9. - Vaclav Kotesovec, Mar 25 2010 MATHEMATICA CoefficientList[Series[x (64 x^15 - 376 x^14 + 760 x^13 - 650 x^12 + 1478 x^11 - 6838 x^10 + 15166 x^9 - 17006 x^8 + 8858 x^7 - 462 x^6 - 2109 x^5 + 1333 x^4 + 1274 x^3 + 70 x^2 + 117 x + 1) / (1 - x)^9, {x, 0, 40}], x] (* Vincenzo Librandi, May 27 2013 *) CROSSREFS A061994, A172127, A172135, A172137, A172138. Sequence in context: A318626 A104678 A154093 * A194717 A002953 A216588 Adjacent sequences:  A172136 A172137 A172138 * A172140 A172141 A172142 KEYWORD nonn AUTHOR Vaclav Kotesovec, Jan 26 2010 STATUS approved

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Last modified October 22 19:53 EDT 2019. Contains 328319 sequences. (Running on oeis4.)