A011910 a(n) = floor( n*(n-1)*(n-2)/28 ).

0, 0, 0, 0, 0, 2, 4, 7, 12, 18, 25, 35, 47, 61, 78, 97, 120, 145, 174, 207, 244, 285, 330, 379, 433, 492, 557, 626, 702, 783, 870, 963, 1062, 1169, 1282, 1402, 1530, 1665, 1807, 1958, 2117, 2284, 2460, 2644, 2838, 3040, 3252, 3474, 3706, 3948, 4200, 4462, 4735, 5019, 5315, 5621, 5940, 6270, 6612, 6966, 7332, 7712, 8104, 8509, 8928, 9360, 9805, 10265, 10739, 11227

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-3,3,-1).

Crossrefs

Cf. A011886.

Programs

Magma

[Floor((n*(n-1)*(n-2))/28): n in [0..80]]; // Vincenzo Librandi, Feb 27 2014

Maple

A011910:=n->floor(n*(n-1)*(n-2)/28); seq(A011910(n), n=0..80); # Wesley Ivan Hurt, Feb 25 2014

Mathematica

Table[Floor[(n(n-1)(n-2))/28],{n,0,80}] (* Harvey P. Dale, Sep 13 2011 *)

SageMath

[3*binomial(n,3)//14 for n in range(81)] # G. C. Greubel, Oct 19 2024

Formula

a(n) = floor(A007531(n)/28). - Wesley Ivan Hurt, Feb 25 2014

G.f.: x^5*(2-2*x+x^2+x^3-x^4+2*x^6-x^7+x^9-x^10+2*x^11-2*x^12+2*x^13+x^19+ x^21-2*x^22+3*x^23-2*x^24+x^25)/((1-x)^4*(1+x)*(1+x^2)*(1-x+x^2-x^3+x^4-x^5+x^6)*(1+x+x^2+x^3+x^4+x^5+x^6)*(1-x^2+x^4-x^6+x^8-x^10+x^12)). - Peter J. C. Moses, Jun 02 2014