OFFSET
0,6
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1,1,-4,6,-4,1).
FORMULA
a(n) = 4 * A011795(n).
From R. J. Mathar, Apr 15 2010: (Start)
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + a(n-5) - 4*a(n-6) + 6*a(n-7) - 4*a(n-8) + a(n-9).
G.f.: 4*x^5*(1-x+x^2) / ((1-x)^5*(1+x+x^2+x^3+x^4) ). (End)
MATHEMATICA
CoefficientList[Series[4*x^5*(1-x+x^2)/((1-x)^4*(1-x^5)), {x, 0, 60}], x] (* Vincenzo Librandi, Jun 19 2012 *)
LinearRecurrence[{4, -6, 4, -1, 1, -4, 6, -4, 1}, {0, 0, 0, 0, 0, 4, 12, 28, 56}, 60] (* Harvey P. Dale, Nov 13 2017 *)
Floor[4*Binomial[Range[0, 60], 4]/5] (* G. C. Greubel, Oct 27 2024 *)
PROG
(Magma) [Floor(n*(n-1)*(n-2)*(n-3)/30): n in [0..60]]; // Vincenzo Librandi, Jun 19 2012
(SageMath) [4*binomial(n, 4)//5 for n in range(61)] # G. C. Greubel, Oct 27 2024
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
STATUS
approved