login
A259736
Number of (n+2) X (2+2) 0..1 arrays with each 3 X 3 subblock having clockwise perimeter pattern 00010101 or 01010101.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jul 04 2015
STATUS
approved