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

Author

N. J. A. Sloane

Keywords

• nonn
• easy

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).

Crossrefs

Sequences of the form floor(24*binomial(n,4)/m): A052762 (m=1), A033486 (m=2), A162668 (m=3), A033487 (m=4), this sequence (m=5), A033488 (m=6), A011917 (m=7), A050534 (m=8), A011919 (m=9), 2*A011930 (m=10), A011921 (m=11), A034827 (m=12), A011923 (m=13), A011924 (m=14), A011925 (m=15), A011926 (m=16), A011927 (m=17), A011928 (m=18), A011929 (m=19), A011930 (m=20), A011931 (m=21), A011932 (m=22), A011933 (m=23), A000332 (m=24), A011935 (m=25),A011936 (m=26), A011937 (m=27), A011938 (m=28), A011939 (m=29), A011940 (m=30), A011941 (m=31), A011942 (m=32), A011795 (m=120).

Programs

Magma

[Floor(n*(n-1)*(n-2)*(n-3)/5): n in [0..60]]; // Vincenzo Librandi, Jun 19 2012

Mathematica

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

SageMath

[24*binomial(n,4)//5 for n in range(61)] # G. C. Greubel, Oct 20 2024

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

a(n) = 4*A011930(n). - G. C. Greubel, Oct 20 2024

Extensions

More terms from Stefan Steinerberger, Apr 10 2006

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