A259736 Number of (n+2) X (2+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00010101 or 01010101.

22, 36, 74, 136, 230, 414, 760, 1356, 2414, 4348, 7820, 14004, 25114, 45102, 80930, 145162, 260480, 467442, 838696, 1504818, 2700182, 4845016, 8693348, 15598530, 27988744, 50220456, 90110864, 161686882, 290116538, 520558722, 934043350

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

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

Empirical g.f.: 2*x*(11 + 7*x + 19*x^2 + 9*x^3) / (1 - x - 2*x^3 - x^4). - Colin Barker, Dec 26 2018

Example

Some solutions for n=4:
..1..0..1..0....1..0..1..0....0..1..0..0....0..1..0..1....1..0..1..0
..0..1..0..1....0..1..0..0....1..0..0..0....1..0..1..0....0..1..0..0
..1..0..1..0....1..0..1..0....0..1..0..1....0..1..0..0....1..0..1..0
..0..1..0..0....0..1..0..1....1..0..1..0....1..0..1..0....0..1..0..1
..0..0..1..0....0..0..1..0....0..1..0..0....0..1..0..1....1..0..0..0
..0..1..0..1....0..1..0..1....0..0..1..0....0..0..1..0....0..1..0..0

Crossrefs

Column 2 of A259742.

Sequence in context: A233404 A167277 A084141 * A082261 A335373 A337460

Adjacent sequences: A259733 A259734 A259735 * A259737 A259738 A259739

Keyword

nonn

Author

R. H. Hardin, Jul 04 2015

Status

approved