A250447 Number of (n+1)X(1+1) 0..2 arrays with nondecreasing min(x(i,j),x(i,j-1)) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

44, 217, 1000, 4535, 20242, 89677, 395240, 1736779, 7617286, 33369545, 146077396, 639173575, 2795963426, 12228336613, 53475556816, 233837032739, 1022474657182, 4470747289345, 19547912489996, 85470468806527, 373705021918234

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 3*a(n-2) - 20*a(n-3) + 6*a(n-4) + 12*a(n-5).

Empirical g.f.: x*(44 - 47*x - 170*x^2 + 66*x^3 + 108*x^4) / ((1 - x)*(1 - 2*x - 2*x^2)*(1 - 3*x - 6*x^2)). - Colin Barker, Nov 14 2018

Example

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

Crossrefs

Column 1 of A250454.

Sequence in context: A215677 A122235 A250454 * A233949 A233942 A122245

Adjacent sequences: A250444 A250445 A250446 * A250448 A250449 A250450

Keyword

nonn

Author

R. H. Hardin, Nov 23 2014

Status

approved