A253429 Number of (n+1) X (2+1) 0..1 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally, vertically and ne-to-sw antidiagonally.

39, 58, 73, 108, 180, 324, 612, 1188, 2340, 4644, 9252, 18468, 36900, 73764, 147492, 294948, 589860, 1179684, 2359332, 4718628, 9437220, 18874404, 37748772, 75497508, 150994980, 301989924, 603979812, 1207959588, 2415919140, 4831838244

Offset

1,1

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) for n>5.

Empirical: a(n) = 9*2^(n-1) + 36 for n>3.

Empirical g.f.: x*(39 - 59*x - 23*x^2 + 5*x^3 + 2*x^4) / ((1 - x)*(1 - 2*x)). - Colin Barker, Dec 12 2018

Example

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

Crossrefs

Column 2 of A253435.

Sequence in context: A116281 A168530 A253436 * A338794 A050780 A039353

Adjacent sequences: A253426 A253427 A253428 * A253430 A253431 A253432

Keyword

nonn

Author

R. H. Hardin, Dec 31 2014

Status

approved