A011917 [ n(n-1)(n-2)(n-3)/7 ].

0, 0, 0, 0, 3, 17, 51, 120, 240, 432, 720, 1131, 1697, 2451, 3432, 4680, 6240, 8160, 10491, 13289, 16611, 20520, 25080, 30360, 36432, 43371, 51257, 60171, 70200, 81432, 93960, 107880, 123291, 140297, 159003

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1,0,0,1,-4,6,-4,1).

Programs

Mathematica

Table[Floor[Times@@(n-Range[0,3])/7],{n,0,40}] (* or *) LinearRecurrence[ {4,-6,4,-1,0,0,1,-4,6,-4,1},{0,0,0,0,3,17,51,120,240,432,720},50] (* Harvey P. Dale, Oct 20 2016 *)

PARI

a(n)=n*(n-1)*(n-2)*(n-3)\7 \\ Charles R Greathouse IV, Oct 18 2022

Formula

a(n) = +4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4) +a(n-7) -4*a(n-8) +6*a(n-9) -4*a(n-10) +a(n-11). G.f.: x^4*(3+5*x+x^2+6*x^3+x^4+5*x^5+3*x^6) / ( (1-x)^5*(1+x+x^2+x^3+x^4+x^5+x^6) ). - R. J. Mathar, Apr 15 2010