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 A026054 dot_product(n,n-1,...2,1).(3,4,...,n,1,2). 5
 13, 28, 50, 80, 119, 168, 228, 300, 385, 484, 598, 728, 875, 1040, 1224, 1428, 1653, 1900, 2170, 2464, 2783, 3128, 3500, 3900, 4329, 4788, 5278, 5800, 6355, 6944, 7568, 8228, 8925, 9660, 10434, 11248, 12103, 13000, 13940, 14924, 15953, 17028, 18150, 19320, 20539, 21808, 23128, 24500, 25925 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 3..1000 Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA a(n) = n*(n^2+9*n-10)/6. G.f.: x^3*(13-24*x+16*x^2-4*x^3)/(1-x)^4. [Colin Barker, Sep 17 2012] MATHEMATICA Table[Range[n, 1, -1].RotateLeft[Range[n], 2], {n, 3, 60}] (* or *) LinearRecurrence[ {4, -6, 4, -1}, {13, 28, 50, 80}, 60] (* Harvey P. Dale, Oct 14 2012 *) Drop[CoefficientList[Series[x (13 - 24 x + 16 x^2 - 4 x^3)/(1 - x)^4, {x, 0, 60}], x], 1] (* Vincenzo Librandi, Oct 17 2013 *) PROG (MAGMA) [n*(n^2+9*n-10)/6: n in [3..60]]; // Vincenzo Librandi, Oct 17 2013 CROSSREFS A023551(n+1) + 4. Column 2 of triangle A094415. Essentially the same as A060488. - Vladeta Jovovic, Jun 15 2006 Sequence in context: A098847 A161453 A038597 * A281476 A001291 A018974 Adjacent sequences:  A026051 A026052 A026053 * A026055 A026056 A026057 KEYWORD nonn,easy AUTHOR EXTENSIONS Closed-form formula corrected by Colin Barker, Sep 17 2012 STATUS approved

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Last modified March 20 13:18 EDT 2019. Contains 321345 sequences. (Running on oeis4.)