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A011915 a(n) = floor(n(n-1)(n-2)(n-3)/5). 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
LINKS
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
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Stefan Steinerberger, Apr 10 2006
Zero added in front by R. J. Mathar, Apr 15 2010
STATUS
approved

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Last modified April 25 10:01 EDT 2024. Contains 371967 sequences. (Running on oeis4.)