A251221 Number of (n+1) X (1+1) 0..1 arrays with no 2 X 2 subblock having the minimum of its diagonal elements greater than the absolute difference of its antidiagonal elements.

14, 49, 171, 597, 2084, 7275, 25396, 88654, 309479, 1080349, 3771351, 13165272, 45958169, 160433700, 560052166, 1955065729, 6824867819, 23824682749, 83168718156, 290330652147, 1013504710004, 3538006716150, 12350698916311

Offset: 1

Author

R. H. Hardin, Nov 30 2014

Keywords

• nonn

Comments

Column 1 of A251228.

Examples

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

Links

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

Crossrefs

Cf. A251228.

Formula

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

Empirical g.f.: x*(14 + 7*x - 4*x^2) / (1 - 3*x - 2*x^2 + x^3). - Colin Barker, Feb 25 2018