A011909 a(n) = floor( n*(n-1)*(n-2)/27 ).

0, 0, 0, 0, 0, 2, 4, 7, 12, 18, 26, 36, 48, 63, 80, 101, 124, 151, 181, 215, 253, 295, 342, 393, 449, 511, 577, 650, 728, 812, 902, 998, 1102, 1212, 1329, 1454, 1586, 1726, 1874, 2030, 2195, 2368, 2551, 2742, 2943

Offset

0,6

Links

Table of n, a(n) for n=0..44.

Index entries for linear recurrences with constant coefficients, signature (4, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 4, -1).

Formula

G.f.: x^5 (1-x+x^2) (2-2 x-x^2+3 x^3-2 x^4+3 x^6-3 x^7+2 x^9-x^10-x^11+3 x^12-2 x^13-x^14+3 x^15-2 x^16+2 x^18-2 x^19+x^20)/((-1+x)^4 (1+x^3+x^6) (1+x^9+x^18)). - Peter J. C. Moses, Jun 02 2014

Mathematica

Table[Floor[n(n-1)(n-2)/27], {n, 0, 60}] (* or *) LinearRecurrence[{4, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 3, 3, -6, 4, -1}, {0, 0, 0, 0, 0, 2, 4, 7, 12, 18, 26, 36, 48, 63, 80, 101, 124, 151, 181, 215, 253, 295, 342, 393, 449, 511, 577, 650}, 60] (* Harvey P. Dale, Jun 12 2023 *)

Crossrefs

Sequence in context: A005521 A135901 A124197 * A065962 A173722 A049703

Adjacent sequences: A011906 A011907 A011908 * A011910 A011911 A011912

Keyword

nonn

Author

N. J. A. Sloane.

Status

approved