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

1,1

Comments

Column 1 of A251228.

Links

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

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

Example

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

Crossrefs

Cf. A251228.

Sequence in context: A367360 A308834 A084049 * A302467 A303249 A215569

Adjacent sequences: A251218 A251219 A251220 * A251222 A251223 A251224

Keyword

nonn

Author

R. H. Hardin, Nov 30 2014

Status

approved