A268744 Number of n X 2 binary arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.

4, 11, 32, 89, 244, 659, 1760, 4657, 12228, 31899, 82752, 213641, 549236, 1406755, 3591232, 9140833, 23204612, 58765099, 148496608, 374496953, 942729588, 2369172915, 5944748064, 14895231121, 37272007108, 93149401019, 232527917312

Offset: 1

Author

R. H. Hardin, Feb 12 2016

Keywords

• nonn

Comments

Column 2 of A268750.

Examples

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

Links

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

Crossrefs

Cf. A268750.

Formula

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

Empirical g.f.: x*(4 - 5*x - 4*x^2 - x^3) / (1 - 2*x - x^2)^2. - Colin Barker, Mar 21 2018