A011842 a(n) = floor(n(n-1)(n-2)/24).

0, 0, 0, 0, 1, 2, 5, 8, 14, 21, 30, 41, 55, 71, 91, 113, 140, 170, 204, 242, 285, 332, 385, 442, 506, 575, 650, 731, 819, 913, 1015, 1123, 1240, 1364, 1496, 1636, 1785, 1942, 2109, 2284, 2470, 2665, 2870, 3085

Offset

0,6

Links

Table of n, a(n) for n=0..43.

Index entries for linear recurrences with constant coefficients, signature (3, -3, 1, 0, 0, 0, 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-8) - 3*a(n-9) + 3*a(n-10) - a(n-11).

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

a(n) = floor(binomial(n+1,4)/(n+1)). - Gary Detlefs, Nov 23 2011

Maple

seq(floor(binomial(n, 3)/4), n=0..43); # Zerinvary Lajos, Jan 12 2009

Crossrefs

A column of triangle A011847.

Sequence in context: A274523 A165189 A358055 * A000094 A182377 A327380

Adjacent sequences: A011839 A011840 A011841 * A011843 A011844 A011845

Keyword

nonn

Author

N. J. A. Sloane

Status

approved