A011923 a(n) = floor(n*(n-1)*(n-2)*(n-3)/13).

0, 0, 0, 0, 1, 9, 27, 64, 129, 232, 387, 609, 913, 1320, 1848, 2520, 3360, 4393, 5649, 7155, 8944, 11049, 13504, 16347, 19617, 23353, 27600, 32400, 37800, 43848, 50593, 58089, 66387, 75544, 85617, 96664, 108747, 121929, 136273, 151848, 168720, 186960, 206640, 227833

Offset

0,6

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1,0,0,0,0,0,0,0,0,1,-4,6,-4,1).

Formula

From Chai Wah Wu, Aug 02 2020: (Start)

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + a(n-13) - 4*a(n-14) + 6*a(n-15) - 4*a(n-16) + a(n-17) for n > 16.

G.f.: x^4*(-x^12 - 5*x^11 + 3*x^10 - 6*x^9 - x^7 - 4*x^6 - x^5 - 6*x^3 + 3*x^2 - 5*x - 1)/(x^17 - 4*x^16 + 6*x^15 - 4*x^14 + x^13 - x^4 + 4*x^3 - 6*x^2 + 4*x - 1). (End)

Mathematica

A011923[n_] := Quotient[n*(n-1)*(n-2)*(n-3), 13]; Array[A011923, 50, 0] (* Paolo Xausa, Jun 05 2026 *)

Prog

(PARI) a(n)=n*(n-1)*(n-2)*(n-3)\13 \\ Charles R Greathouse IV, Oct 18 2022

Crossrefs

Sequence in context: A271990 A153237 A256327 * A029875 A335671 A337628

Adjacent sequences: A011920 A011921 A011922 * A011924 A011925 A011926

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

More terms from Paolo Xausa, Jun 05 2026

Status

approved