A250751 Number of (n+1) X (4+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing x(i,j)+x(i-1,j) in the j direction.

203, 663, 2123, 6663, 20603, 63063, 191723, 580263, 1751003, 5273463, 15861323, 47665863, 143161403, 429811863, 1290090923, 3871583463, 11617371803, 34857358263, 104582560523, 313768653063, 941347902203, 2824127592663

Offset: 1

Author

R. H. Hardin, Nov 27 2014

Keywords

• nonn

Examples

			Some solutions for n=4:
..2..2..2..2..2....2..2..2..2..2....1..1..1..1..1....0..0..0..0..0
..2..2..2..2..2....1..1..1..1..1....1..1..1..1..1....0..0..0..0..0
..1..1..1..1..1....0..1..1..1..1....1..2..2..2..2....0..0..0..0..0
..0..0..0..0..0....1..2..2..2..2....0..1..1..1..1....1..1..1..1..2
..0..0..0..1..2....0..1..2..2..2....0..1..1..1..2....1..1..1..1..2
		

Links

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

Crossrefs

Column 4 of A250755.

Formula

Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3); a(n) = (180*3^n - 80*2^n + 26)/2.

Empirical g.f.: x*(7 - 9*x)*(29 - 42*x) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Nov 17 2018