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 A011903 a(n) = floor(n*(n-1)*(n-2)/21). 1
 0, 0, 0, 0, 1, 2, 5, 10, 16, 24, 34, 47, 62, 81, 104, 130, 160, 194, 233, 276, 325, 380, 440, 506, 578, 657, 742, 835, 936, 1044, 1160, 1284, 1417, 1558, 1709, 1870, 2040, 2220, 2410, 2611, 2822, 3045, 3280 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,1,-3,3,-1). [From R. J. Mathar, Apr 15 2010] FORMULA From R. J. Mathar, Apr 15 2010: (Start) a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-7) - 3*a(n-8) + 3*a(n-9) - a(n-10). G.f.: x^4*(x^5-x^4+2*x^2-x+1) / ( (-1+x)^4*(x^6+x^5+x^4+x^3+x^2+x+1) ). (End) MATHEMATICA CoefficientList[Series[x^4*(x^5-x^4+2*x^2-x+1)/((-1+x)^4*(x^6+x^5+x^4+ 5x^3+x^2+x+1)), {x, 0, 10}], x] (* Vincenzo Librandi, Jul 07 2012 *) PROG (MAGMA) [Floor(n*(n-1)*(n-2)/21): n in [0..50]]; // Vincenzo Librandi, Jul 07 2012 CROSSREFS Sequence in context: A267159 A084587 A001859 * A078435 A049815 A047992 Adjacent sequences:  A011900 A011901 A011902 * A011904 A011905 A011906 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified March 21 01:18 EDT 2019. Contains 321356 sequences. (Running on oeis4.)