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A011890
a(n) = floor( n*(n-1)*(n-2)/8 ).
2
0, 0, 0, 0, 3, 7, 15, 26, 42, 63, 90, 123, 165, 214, 273, 341, 420, 510, 612, 726, 855, 997, 1155, 1328, 1518, 1725, 1950, 2193, 2457, 2740, 3045, 3371, 3720, 4092, 4488, 4908, 5355, 5827, 6327, 6854, 7410, 7995, 8610, 9255, 9933, 10642, 11385, 12161, 12972, 13818, 14700
OFFSET
0,5
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*(3-2*x+3*x^2-x^3+2*x^4+x^6)/((1-x)^4*(1+x)*(1+x^2)*(1+x^4)). (End)
MATHEMATICA
Floor[6*Binomial[Range[0, 50], 3]/8] (* G. C. Greubel, Oct 06 2024 *)
PROG
(Magma) [Floor(6*Binomial(n, 3)/8): n in [0..50]]; // G. C. Greubel, Oct 06 2024
(SageMath) [6*binomial(n, 3)//8 for n in range(51)] # G. C. Greubel, Oct 06 2024
CROSSREFS
Cf. A011886.
Sequence in context: A328688 A291651 A078869 * A131076 A001648 A051054
KEYWORD
nonn
EXTENSIONS
a(41) onwards from G. C. Greubel, Oct 06 2024
STATUS
approved