A011915 a(n) = floor(n(n-1)(n-2)(n-3)/5).

0, 0, 0, 0, 4, 24, 72, 168, 336, 604, 1008, 1584, 2376, 3432, 4804, 6552, 8736, 11424, 14688, 18604, 23256, 28728, 35112, 42504, 51004, 60720, 71760, 84240, 98280, 114004, 131544, 151032, 172608, 196416, 222604, 251328, 282744, 317016, 354312

Offset

0,5

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*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^4*(1+2*x+2*x^3+x^4) / ( (1-x)^5*(1+x+x^2+x^3+x^4) ). - R. J. Mathar, Apr 15 2010

Mathematica

Table[Floor[n(n - 1)(n - 2)(n - 3)/5], {n, 1, 60}] (* Stefan Steinerberger, Apr 10 2006 *)
CoefficientList[Series[4*x^4*(1+2*x+2*x^3+x^4)/((1-x)^5*(1+x+x^2+x^3+x^4)), {x, 0, 50}], x] (* Vincenzo Librandi, Jun 19 2012

Prog

(Magma) [Floor(n*(n - 1)*(n - 2)*(n - 3)/5): n in [0..45]]; // Vincenzo Librandi, Jun 19 2012

Crossrefs

Sequence in context: A364600 A181617 A261256 * A199904 A250132 A025220

Adjacent sequences: A011912 A011913 A011914 * A011916 A011917 A011918

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

More terms from Stefan Steinerberger, Apr 10 2006

Zero added in front by R. J. Mathar, Apr 15 2010

Status

approved