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

1,1

Comments

Column 2 of A268750.

Links

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

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

Example

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

Crossrefs

Cf. A268750.

Sequence in context: A319918 A034754 A345029 * A038747 A052545 A183114

Adjacent sequences: A268741 A268742 A268743 * A268745 A268746 A268747

Keyword

nonn

Author

R. H. Hardin, Feb 12 2016

Status

approved