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
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.: x^4*(x^4+2*x^3+2*x+1) / ((1-x)^5*(x^4+x^3+x^2+x+1)). (End)
MATHEMATICA
CoefficientList[Series[x^4*(x^4+2*x^3+2*x+1)/((1-x)^5*(x^4+x^3+x^2+x+1)), {x, 0, 50}], x] (* Vincenzo Librandi, Jun 19 2012 *)
Table[Floor[n(n-1)(n-2)(n-3)/20], {n, 0, 40}] (* or *) LinearRecurrence[ {4, -6, 4, -1, 1, -4, 6, -4, 1}, {0, 0, 0, 0, 1, 6, 18, 42, 84}, 40] (* Harvey P. Dale, Apr 08 2013 *)
PROG
(Magma) [Floor(n*(n-1)*(n-2)*(n-3)/20 ): n in [0..40]]; // Vincenzo Librandi, Jun 19 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved