A183344 Number of n X 2 binary arrays with each 1 adjacent to exactly one 0 vertically and one 0 horizontally.

1, 7, 9, 17, 33, 59, 109, 201, 369, 679, 1249, 2297, 4225, 7771, 14293, 26289, 48353, 88935, 163577, 300865, 553377, 1017819, 1872061, 3443257, 6333137, 11648455, 21424849, 39406441, 72479745, 133311035, 245197221, 450988001, 829496257

Offset

1,2

Comments

Column 2 of A183352.

Links

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

Formula

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

Empirical g.f.: x*(1 + 6*x + x^2) / (1 - x - x^2 - x^3). - Colin Barker, Mar 27 2018

Example

Some solutions for 5 X 2:
..0..1....0..0....0..0....0..0....0..1....0..0....0..0....1..0....0..0....1..0
..0..0....0..0....0..0....1..0....0..0....1..0....1..0....0..0....0..0....0..0
..1..0....0..0....1..0....1..0....0..1....1..0....1..0....0..1....0..0....1..0
..1..0....0..0....1..0....0..0....0..1....0..0....0..0....0..1....0..0....1..0
..0..1....0..1....0..1....0..0....0..0....0..1....1..0....1..0....1..0....0..0

Crossrefs

Cf. A183352.

Sequence in context: A366526 A022321 A194830 * A255830 A256613 A116484

Adjacent sequences: A183341 A183342 A183343 * A183345 A183346 A183347

Keyword

nonn

Author

R. H. Hardin, Jan 04 2011

Status

approved