A183314 Number of n X 2 binary arrays with an element zero only if there are an even number of ones to its left and an even number of ones above it.

3, 6, 13, 27, 57, 119, 250, 523, 1097, 2297, 4815, 10086, 21137, 44283, 92793, 194419, 407378, 853559, 1788481, 3747361, 7851867, 16451910, 34471669, 72228171, 151339401, 317100335, 664418698, 1392152131, 2916968489, 6111905849

Offset: 1

Author

R. H. Hardin, Jan 03 2011

Keywords

• nonn

Comments

Column 2 of A183322.

Is this related to A131246?

Examples

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

Links

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

Crossrefs

Cf. A131246, A183322.

Formula

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

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