A251262 Number of (n+1) X (2+1) 0..1 arrays with no 2 X 2 subblock having x11-x00 less than x10-x01.

26, 114, 480, 2058, 8812, 37772, 161906, 694042, 2975162, 12753740, 54671978, 234364684, 1004661088, 4306723662, 18461816670, 79141059954, 339257370296, 1454309095546, 6234249070708, 26724622430876, 114561583275826

Offset

1,1

Links

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

Formula

Empirical: a(n) = 5*a(n-1) - 2*a(n-2) - 5*a(n-3) + 2*a(n-4).

Empirical g.f.: 2*x*(13 - 8*x - 19*x^2 + 8*x^3) / (1 - 5*x + 2*x^2 + 5*x^3 - 2*x^4). - Colin Barker, Nov 27 2018

Example

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

Crossrefs

Column 2 of A251268.

Sequence in context: A262756 A262476 A156385 * A221570 A100161 A100162

Adjacent sequences: A251259 A251260 A251261 * A251263 A251264 A251265

Keyword

nonn

Author

R. H. Hardin, Dec 01 2014

Status

approved