A066406 a(n) = 2^n*(3^n-3).

0, 24, 192, 1248, 7680, 46464, 279552, 1678848, 10076160, 60463104, 362790912, 2176770048, 13060669440, 78364114944, 470184886272, 2821109710848, 16926659051520, 101559955881984, 609359738437632, 3656158436917248, 21936950634086400, 131621703829684224

Offset: 1

Author

N. J. A. Sloane, Dec 25 2001

Keywords

• nonn
• easy

Comments

Number of orthogonal arrays OA(4,n,2,1).

Links

• Harry J. Smith, Table of n, a(n) for n = 1..150
• J.-Z. Zhang, Z.-S. You and Z.-L. Li, Enumeration of binary orthogonal arrays of strength 1, Discrete Math., 239 (2000), 191-198.
• Index entries for linear recurrences with constant coefficients, signature (8,-12).

Programs

Mathematica

Table[2^n(3^n-3),{n,30}] (* or *) LinearRecurrence[{8,-12},{0,24},30] (* Harvey P. Dale, Jul 28 2019 *)

PARI

a(n) = { 2^n*(3^n - 3) } \\ Harry J. Smith, Feb 13 2010

PARI

concat(0, Vec(24*x^2/((2*x-1)*(6*x-1)) + O(x^30))) \\ Colin Barker, Oct 20 2015

Formula

From Colin Barker, Oct 20 2015: (Start)

a(n) = 8*a(n-1)-12*a(n-2).

G.f.: 24*x^2 / ((2*x-1)*(6*x-1)). (End)