A186055 Number of (n+2) X 3 binary arrays with each 3 X 3 subblock having a positive determinant.

87, 267, 792, 2328, 6915, 20475, 60588, 179442, 531306, 1573062, 4657767, 13791129, 40833855, 120904779, 357985743, 1059956097, 3138413982, 9292498818, 27514066965, 81466129305, 241212255042, 714202974702, 2114676514230

Offset

1,1

Comments

Column 1 of A186063.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 2*a(n-1) + a(n-2) + 6*a(n-3) - 2*a(n-4) + 2*a(n-5) - 3*a(n-6) + 2*a(n-7).

Empirical g.f.: 3*x*(29 + 31*x + 57*x^2 - 15*x^3 + 13*x^4 - 25*x^5 + 22*x^6) / (1 - 2*x - x^2 - 6*x^3 + 2*x^4 - 2*x^5 + 3*x^6 - 2*x^7). - Colin Barker, Apr 17 2018

Example

Some solutions for 4 X 3:
..0..1..0....0..1..0....0..0..1....0..0..1....1..1..0....1..0..0....1..0..1
..0..1..1....0..1..1....1..0..0....1..1..0....0..1..0....0..1..0....1..1..1
..1..0..0....1..0..0....0..1..1....0..1..1....1..1..1....1..0..1....0..1..1
..1..1..0....0..1..0....0..0..1....1..0..1....1..0..0....1..1..0....0..0..1

Crossrefs

Cf. A186063.

Sequence in context: A008899 A008879 A186063 * A243580 A219723 A033631

Adjacent sequences: A186052 A186053 A186054 * A186056 A186057 A186058

Keyword

nonn

Author

R. H. Hardin, Feb 11 2011

Status

approved