A011912 a(n) = floor(n*(n-1)*(n-2)/30).

0, 0, 0, 0, 0, 2, 4, 7, 11, 16, 24, 33, 44, 57, 72, 91, 112, 136, 163, 193, 228, 266, 308, 354, 404, 460, 520, 585, 655, 730, 812, 899, 992, 1091, 1196, 1309, 1428, 1554, 1687, 1827, 1976, 2132, 2296, 2468, 2648

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,-3,1,0,1,-3,3,-1).

Formula

From R. J. Mathar, Apr 15 2010: (Start)

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-5) - 3*a(n-6) + 3*a(n-7) - a(n-8).

G.f.: x^5*(x^2-2*x+2) / ( (-1+x)^4*(x^4+x^3+x^2+x+1) ). (End)

Maple

seq(floor(binomial(n, 3)/5), n=0..43); # Zerinvary Lajos, Jan 12 2009

Mathematica

Table[Floor[(n(n-1)(n-2))/30], {n, 0, 50}] (* or *) LinearRecurrence[ {3, -3, 1, 0, 1, -3, 3, -1}, {0, 0, 0, 0, 0, 2, 4, 7}, 50] (* Harvey P. Dale, Jun 20 2011 *)
CoefficientList[Series[x^5*(x^2-2*x+2)/((-1+x)^4*(x^4+x^3+x^2+x+1)), {x, 0, 50}], x] (* Vincenzo Librandi, Jul 07 2012 *)

Prog

(Magma) [Floor(n*(n-1)*(n-2)/30): n in [0..50]]; // Vincenzo Librandi, Jul 07 2012

Crossrefs

Sequence in context: A320591 A129339 A196719 * A063676 A099385 A331387

Adjacent sequences: A011909 A011910 A011911 * A011913 A011914 A011915

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved