A011905 a(n) = floor( n*(n-1)*(n-2)/23 ).

0, 0, 0, 0, 1, 2, 5, 9, 14, 21, 31, 43, 57, 74, 94, 118, 146, 177, 212, 252, 297, 346, 401, 462, 528, 600, 678, 763, 854, 953, 1059, 1172, 1293, 1423, 1561, 1707, 1862, 2026, 2200, 2384, 2577, 2780, 2994, 3219, 3454, 3701, 3960, 4230, 4512, 4806, 5113, 5432, 5765, 6111, 6470, 6843, 7231, 7633, 8049, 8480, 8926, 9388, 9866, 10359, 10868, 11394, 11937, 12496, 13073

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..2000
• Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-3,3,-1).

Crossrefs

Cf. A011886.

Programs

Magma

[Floor(6*Binomial(n,3)/23): n in [0..75]]; // G. C. Greubel, Oct 18 2024

Mathematica

Table[Floor[(n(n-1)(n-2))/23],{n,0,75}] (* Harvey P. Dale, Aug 06 2013 *)

SageMath

[6*binomial(n,3)//23 for n in range(76)] # G. C. Greubel, Oct 18 2024

Formula

G.f.: x^4*(1+x*(-1+x*(2+x*(-1+x^2*(1+(-1+x)*x^2)*(1+x+x^6+x^10+x^13))))) /(1+x*(-3+x*(3+x*(-1+(-1+x)^3*x^20)))). - Peter J. C. Moses, Jun 02 2014

Extensions

More terms added by G. C. Greubel, Oct 18 2024