A183330 Number of n X 2 binary arrays with each 1 adjacent to exactly two 0's.

1, 7, 10, 23, 49, 98, 209, 431, 898, 1871, 3889, 8098, 16849, 35063, 72970, 151847, 316001, 657602, 1368481, 2847839, 5926402, 12332959, 25665121, 53409602, 111146401, 231297767, 481335050, 1001667383, 2084488849, 4337860898

Offset

1,2

Comments

Column 2 of A183335.

Links

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

Formula

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

Empirical g.f.: x*(1 + 6*x + x^2 - 2*x^3) / (1 - x - 2*x^2 - x^3 + x^4). - Colin Barker, Feb 27 2018

Example

Some solutions for 7 X 2:
..0..0....0..0....0..1....1..0....1..0....0..0....1..0....0..0....1..0....0..0
..1..1....0..0....0..0....0..0....0..1....1..0....0..0....1..1....0..0....1..1
..0..0....1..1....1..1....1..1....0..1....1..0....0..0....0..0....1..1....0..0
..1..1....0..0....0..0....0..0....0..0....0..0....1..0....0..0....0..0....0..0
..0..0....1..1....1..1....0..0....1..0....0..0....1..0....0..0....1..1....1..0
..0..0....0..0....0..0....0..0....1..0....0..0....0..0....0..0....0..0....1..0
..1..0....0..0....1..0....0..1....0..0....0..0....0..1....1..0....0..1....0..0

Crossrefs

Cf. A183335.

Sequence in context: A074377 A103119 A054224 * A196316 A134329 A175492

Adjacent sequences: A183327 A183328 A183329 * A183331 A183332 A183333

Keyword

nonn

Author

R. H. Hardin, Jan 03 2011

Status

approved