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 A172225 Number of ways to place 2 nonattacking wazirs on an n X n board. 13
 0, 2, 24, 96, 260, 570, 1092, 1904, 3096, 4770, 7040, 10032, 13884, 18746, 24780, 32160, 41072, 51714, 64296, 79040, 96180, 115962, 138644, 164496, 193800, 226850, 263952, 305424, 351596, 402810, 459420, 521792, 590304 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A wazir is a (fairy chess) leaper [0,1] REFERENCES Christian Poisson, Echecs et mathematiques, Rex Multiplex 29/1990, p.829 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1). FORMULA Explicit formula (Christian Poisson, 1990): a(n) = n(n-1)(n^2+n-4)/2 G.f.: 2x^2*(2x^2-7x-1)/(x-1)^5 [From Vaclav Kotesovec, Mar 25 2010] a(n) = 5*a(n-1)-10*a(n-2)+10*a(n-3)-5*a(n-4)+a(n-5). - Vincenzo Librandi, Apr 30 2013 a(n) = 2*A239352(n). - R. J. Mathar, Jan 09 2018 MATHEMATICA Table[n (n - 1) (n^2 + n - 4) / 2, {n, 40}] (* Vincenzo Librandi, Apr 30 2013 *) PROG (MAGMA) I:=[0, 2, 24, 96, 260]; [n le 5 select I[n] else 5*Self(n-1)-10*Self(n-2)+10*Self(n-3)-5*Self(n-4)+Self(n-5): n in [1..40]]; /* or */ [n*(n-1)*(n^2+n-4)/2: n in [1..40]]; // Vincenzo Librandi, Apr 30 2013 CROSSREFS Cf. A036464, A061995, A172132, A172123, A172137. Sequence in context: A136280 A123831 A138648 * A145889 A212568 A121199 Adjacent sequences:  A172222 A172223 A172224 * A172226 A172227 A172228 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.)