A250462 Number of (n+1)X(2+1) 0..1 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.

31, 134, 557, 2322, 9651, 40124, 166765, 693150, 2880943, 11974176, 49768529, 206854274, 859753523, 3573415396, 14852276117, 61730889542, 256573649655, 1066403520168, 4432319795801, 18422162351626, 76568497150395

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 3*a(n-2) - 10*a(n-3) + 4*a(n-5).

Empirical g.f.: x*(31 + 10*x - 72*x^2 + 2*x^3 + 32*x^4) / ((1 - x)^2*(1 - 2*x - 8*x^2 - 4*x^3)). - Colin Barker, Nov 14 2018

Example

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

Crossrefs

Column 2 of A250468.

Sequence in context: A044363 A044744 A167388 * A123236 A142561 A165568

Adjacent sequences: A250459 A250460 A250461 * A250463 A250464 A250465

Keyword

nonn

Author

R. H. Hardin, Nov 23 2014

Status

approved