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A011908
a(n) = floor( n*(n-1)*(n-2)/26 ).
2
0, 0, 0, 0, 0, 2, 4, 8, 12, 19, 27, 38, 50, 66, 84, 105, 129, 156, 188, 223, 263, 306, 355, 408, 467, 530, 600, 675, 756, 843, 936, 1037, 1144, 1259, 1380, 1510, 1647, 1793, 1946, 2109, 2280, 2460, 2649, 2847, 3056, 3274, 3503, 3741, 3991, 4251, 4523, 4805, 5100, 5406, 5724, 6054, 6396, 6752, 7120
OFFSET
0,6
LINKS
Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,0,0,0,0,0,0,1,-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-13) -3*a(n-14) +3*a(n-15) -a(n-16).
G.f.: x^5*(2-2*x+2*x^2-2*x^3+3*x^4-2*x^5+2*x^6-2*x^7+3*x^8-2*x^9+x^10) / ( (1-x)^3*(1-x^13) ). (End)
MATHEMATICA
Floor[3*Binomial[Range[0, 75], 3]/13] (* G. C. Greubel, Oct 18 2024 *)
PROG
(Magma) [Floor(3*Binomial(n, 3)/13): n in [0..75]]; // G. C. Greubel, Oct 18 2024
(SageMath) [3*binomial(n, 3)//13 for n in range(76)] # G. C. Greubel, Oct 18 2024
CROSSREFS
Cf. A011886.
Sequence in context: A125606 A192078 A136184 * A117455 A277753 A237820
KEYWORD
nonn
EXTENSIONS
More terms added by G. C. Greubel, Oct 18 2024
STATUS
approved