A250799 Number of (2+1) X (n+1) 0..1 arrays with nondecreasing min(x(i,j),x(i,j-1)) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction.

24, 66, 162, 376, 838, 1818, 3868, 8114, 16842, 34680, 70974, 144562, 293356, 593562, 1198210, 2414360, 4857750, 9762474, 19600956, 39324898, 78848794, 158019576, 316560142, 633963266, 1269290508, 2540787978, 5085146898, 10176071704

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 2*x*(12 - 15*x - 3*x^2 + 8*x^3) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Nov 20 2018

Example

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

Crossrefs

Row 2 of A250797.

Sequence in context: A205823 A347314 A175153 * A250791 A043154 A039331

Adjacent sequences: A250796 A250797 A250798 * A250800 A250801 A250802

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved