A011925 a(n) = floor(n*(n-1)*(n-2)*(n-3)/15).

0, 0, 0, 0, 1, 8, 24, 56, 112, 201, 336, 528, 792, 1144, 1601, 2184, 2912, 3808, 4896, 6201, 7752, 9576, 11704, 14168, 17001, 20240, 23920, 28080, 32760, 38001, 43848, 50344, 57536, 65472, 74201, 83776

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).

Programs

Magma

[Floor(n*(n-1)*(n-2)*(n-3)/15): n in [0..45]]; // Vincenzo Librandi, Jun 19 2012

Maple

A011925:=n->floor(n*(n-1)*(n-2)*(n-3)/15); seq(A011925(n), n=0..50); # Wesley Ivan Hurt, Jan 31 2014

Mathematica

CoefficientList[Series[x^4*(x^4+4*x^3-2*x^2+4*x+1)/((1-x)^5*(x^4+x^3+x^2+x+1)),{x,0,50}],x] (* Vincenzo Librandi, Jun 19 2012 *)

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 + 4*x^3 - 2*x^2 + 4*x + 1) / ( (1-x)^5*(x^4 + x^3 + x^2 + x + 1) ). (End)