A232250 Number of (n+1) X (1+1) 0..2 arrays with every element both >= and <= some horizontal or antidiagonal neighbor.

9, 37, 163, 723, 3209, 14245, 63235, 280707, 1246089, 5531525, 24555043, 109002515, 483874057, 2147969733, 9535072003, 42327224963, 187895169801, 834087159397, 3702603905187, 16436262714579, 72962363498889, 323887892265317

Offset

1,1

Links

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

Formula

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

Empirical g.f.: x*(9 + x - 3*x^2 - 3*x^3) / (1 - 4*x - 2*x^2 + x^4). - Colin Barker, Oct 03 2018

Example

Some solutions for n=6:
..1..1....0..0....2..2....1..1....1..1....1..1....2..2....2..2....1..1....0..0
..0..0....1..1....1..1....1..1....0..0....2..2....0..0....1..1....2..2....0..1
..2..2....2..2....2..2....0..0....0..0....1..1....0..2....1..1....2..0....1..2
..1..0....2..1....2..1....1..1....1..2....0..0....2..0....1..2....0..1....2..1
..0..0....1..2....1..2....2..2....2..0....0..0....0..0....2..2....2..2....1..0
..1..2....2..0....2..1....1..0....0..0....0..1....0..0....0..0....2..0....0..0
..2..2....0..0....1..1....0..0....1..1....2..2....0..0....0..0....0..0....0..0

Crossrefs

Column 1 of A232257.

Sequence in context: A026620 A048878 A246315 * A201441 A183327 A364700

Adjacent sequences: A232247 A232248 A232249 * A232251 A232252 A232253

Keyword

nonn

Author

R. H. Hardin, Nov 21 2013

Status

approved