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 A036464 Number of ways to place two nonattacking queens on an n X n board. 19
 0, 0, 8, 44, 140, 340, 700, 1288, 2184, 3480, 5280, 7700, 10868, 14924, 20020, 26320, 34000, 43248, 54264, 67260, 82460, 100100, 120428, 143704, 170200, 200200, 234000, 271908, 314244, 361340, 413540, 471200, 534688, 604384 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 S. Chaiken, C. R. H. Hanusa and T. Zaslavsky, A q-queens problem I. General theory, January 26, 2013. - N. J. A. Sloane, Feb 16 2013 S. Chaiken, C. R. H. Hanusa and T. Zaslavsky, A q-Queens Problem. IV. Queens, Bishops, Nightriders (and Rooks), arXiv:1609.00853 [math.CO], Sep 03 2016. V. Kotesovec, Non-attacking chess pieces I. Rivin, I. Vardi and P. Zimmermann, The n-queens problem, Amer. Math. Monthly, 101 (1994), 629-639. Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1). FORMULA a(n) = C(n, 3)*(3*n-1). G.f.: 4*x^3*(2+x)/(1-x)^5. - Colin Barker, May 02 2012 a(n) = 2*sum_{i=1..n-2} i(i + 1)^2. - Wesley Ivan Hurt, Mar 18 2014 E.g.f.: (exp(x) * x^3 * (8 + 3*x))/6. - Vaclav Kotesovec, Feb 15 2015 For n>0, a(n) = A163102(n-1) - A006331(n-1). - Antal Pinter, Sep 20 2015 MAPLE f:=n->n^4/2 - 5*n^3/3 + 3*n^2/2 - n/3; [seq(f(n), n=1..200)]; # N. J. A. Sloane, Feb 16 2013 MATHEMATICA f[k_] := 2 k; t[n_] := Table[f[k], {k, 1, n}] a[n_] := SymmetricPolynomial[2, t[n]] Table[a[n], {n, 2, 50}] (* A036464 *) Table[a[n]/4, {n, 2, 50}] (* A000914 *) (* Clark Kimberling, Dec 31 2011 *) CoefficientList[Series[4 x^2 (2 + x) / (1-x)^5, {x, 0, 40}], x] (* Vincenzo Librandi, May 02 2013 *) LinearRecurrence[{5, -10, 10, -5, 1}, {0, 0, 8, 44, 140}, 50] (* Harvey P. Dale, Mar 26 2015 *) CROSSREFS Cf. A047659, A061994, A108792, A176186, A178721. Column k=2 of A348129. Sequence in context: A316466 A100583 A261996 * A000938 A252871 A307044 Adjacent sequences: A036461 A036462 A036463 * A036465 A036466 A036467 KEYWORD nonn,easy,nice AUTHOR Robert G. Wilson v, Raymond Bush (c17h21no4(AT)hotmail.com), Kirk Conely, N. J. A. Sloane STATUS approved

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