A183631 Number of (n+1) X 9 0..2 arrays with every 2 X 2 subblock summing to 4.

20709, 22767, 26901, 35223, 52029, 86127, 155781, 299463, 599949, 1240287, 2639061, 5790903, 13157469, 31079247, 76488741, 196005543, 521132589, 1429667007, 4021576821, 11529919383, 33520173309, 98421387567, 290985935301

Offset

1,1

Comments

Column 8 of A183632.

Links

R. H. Hardin, Table of n, a(n) for n = 1..66

Formula

Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3).

Conjectures from Colin Barker, Mar 31 2018: (Start)

G.f.: 3*x*(6903 - 33829*x + 39366*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)).

a(n) = 3*(6220 + 85*2^(2+n) + 3^n).

(End)

Example

Some solutions for 3 X 9:
  1 2 0 2 0 2 2 0 0      2 1 0 0 1 1 1 2 2
  1 0 2 0 2 0 0 2 2      0 1 2 2 1 1 1 0 0
  1 2 0 2 0 2 2 0 0      2 1 0 0 1 1 1 2 2

Crossrefs

Cf. A183632.

Sequence in context: A372296 A237329 A292021 * A340175 A176771 A223237

Adjacent sequences: A183628 A183629 A183630 * A183632 A183633 A183634

Keyword

nonn

Author

R. H. Hardin, Jan 06 2011

Status

approved