A250811 Number of (n+1) X (7+1) 0..2 arrays with nondecreasing 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.

2025, 8049, 29145, 98481, 318585, 1003089, 3104985, 9507441, 28908345, 87498129, 264041625, 795220401, 2391853305, 7187945169, 21588607065, 64815365361, 194545185465, 583833736209, 1751897569305, 5256485430321, 15771041736825

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3); a(n) = (3016*3^n - 3024*2^n + 1050)/2.

Empirical g.f.: 3*x*(675 - 1367*x + 1042*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Nov 20 2018

Example

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

Crossrefs

Column 7 of A250812.

Sequence in context: A126172 A183999 A360216 * A350869 A031768 A156856

Adjacent sequences: A250808 A250809 A250810 * A250812 A250813 A250814

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved