A185513 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock singular.

31, 143, 593, 2553, 10847, 46303, 197329, 841449, 3587359, 15295151, 65211089, 278030937, 1185395807, 5053987327, 21547889233, 91870352457, 391693178911, 1670000659151, 7120119353681, 30356933960889, 129428088631391

Offset: 1

Author

R. H. Hardin, Jan 29 2011

Keywords

• nonn

Comments

Column 1 of A185521.

Examples

			Some solutions for 3 X 2:
..0..2....0..0....2..1....0..1....2..0....1..0....1..2....2..0....1..1....1..0
..0..0....0..1....2..1....0..0....0..0....1..0....0..0....0..0....0..0....2..0
..1..0....0..2....0..0....1..1....0..2....1..0....0..1....0..0....1..2....2..0
		

Links

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

Crossrefs

Cf. A185521.

Formula

Empirical: a(n) = 4*a(n-1) + 3*a(n-2) - 8*a(n-3).

Empirical g.f.: x*(31 + 19*x - 72*x^2) / (1 - 4*x - 3*x^2 + 8*x^3). - Colin Barker, Apr 16 2018