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%I #17 Feb 20 2018 14:20:39
%S 1,70,406,1168,2948,6576,13122,23808,40168,63996,97344,142516,202072,
%T 278828,375856,496484,644296,823132,1037088,1290516,1588024,1934476,
%U 2334992,2794948,3319976
%N Number of ways to place 4 nonattacking zebras on a 4 X n board.
%C Zebra is a (fairy chess) leaper [2,3].
%H Vincenzo Librandi, <a href="/A172222/b172222.txt">Table of n, a(n) for n = 1..1000</a>
%H V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens and kings on boards of various sizes</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ZebraGraph.html.html">Zebra Graph</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Zebra_(chess)">Zebra (chess)</a>
%F a(n) = 4*(8*n^4 - 48*n^3 + 202*n^2 - 471*n + 507)/3, n>=9.
%F 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
%t 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 *)
%Y Cf. A172139, A061990, A172221.
%K nonn,easy
%O 1,2
%A _Vaclav Kotesovec_, Jan 29 2010
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