A225827 Number of binary pattern classes in the (3,n)-rectangular grid: two patterns are in same class if one of them can be obtained by a reflection or 180-degree rotation of the other.

1, 6, 24, 168, 1120, 8640, 66816, 529920, 4212736, 33632256, 268713984, 2148630528, 17184194560, 137456517120, 1099579785216, 8796367749120, 70369826308096, 562954298720256, 4503616874348544, 36028866141093888, 288230651566489600, 2305844111946547200

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (12,-24,-96,256).

Formula

a(n) = 8*a(n-1) + 8*a(n-2) - 64*a(n-3) - 2^(2n-3) with n>2, with a(0)=1, a(1)=6, a(2)=24.

a(n) = 2^(3n/2-1)*(2^(3n/2-1) + 2^(n/2-1) + 1) if n is even,

a(n) = 2^((3*n-1)/2-1)*(2^((3*n-1)/2) + 2^((n-1)/2) + 3) if n is odd.

G.f.: (1-6*x-24*x^2+120*x^3)/((1-4*x)*(1-8*x)*(1-8*x^2)). [Bruno Berselli, May 17 2013]

Mathematica

LinearRecurrence[{12, -24, -96, 256}, {1, 6, 24, 168}, 20] (* Bruno Berselli, May 17 2013 *)
CoefficientList[Series[(1 - 6 x - 24 x^2 + 120 x^3) / ((1 - 4 x) (1 - 8 x) (1 - 8 x^2)), {x, 0, 40}], x] (* Vincenzo Librandi, Sep 04 2013 *)

Prog

(Magma) I:=[1, 6, 24, 168]; [n le 4 select I[n] else 12*Self(n-1)-24*Self(n-2)-96*Self(n-3)+256*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Sep 04 2013

Crossrefs

A005418 is the number of binary pattern classes in the (1,n)-rectangular grid.

A225826 to A225834 are the numbers of binary pattern classes in the (m,n)-rectangular grid, 1 < m < 11.

A225910 is the table of (m,n)-rectangular grids.

Sequence in context: A232688 A221980 A359693 * A349498 A200904 A293488

Adjacent sequences: A225824 A225825 A225826 * A225828 A225829 A225830

Keyword

nonn,easy

Author

Yosu Yurramendi, May 16 2013

Extensions

More terms from Vincenzo Librandi, Sep 04 2013

Status

approved