A250876 Number of (n+1) X (7+1) 0..3 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.

5518, 27686, 131982, 600070, 2633198, 11264166, 47315662, 196169030, 805653678, 3286063846, 13335635342, 53918745990, 217407726958, 874837394726, 3514985555022, 14106883178950, 56568421653038, 226696485544806

Offset

1,1

Links

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

Formula

Empirical: a(n) = 10*a(n-1) - 35*a(n-2) + 50*a(n-3) - 24*a(n-4); a(n) = (9952*4^n - 9828*3^n + 3024*2^n + 182)/3.

Empirical g.f.: 2*x*(2759 - 13747*x + 24126*x^2 - 13320*x^3) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)). - Colin Barker, Nov 22 2018

Example

Some solutions for n=3:
..3..3..3..3..3..3..3..3....2..3..3..3..3..3..3..3....1..1..1..1..0..0..0..0
..0..2..2..2..2..2..2..2....2..3..3..3..3..3..3..3....0..0..0..0..1..1..1..1
..0..2..2..2..2..3..3..3....0..2..2..2..2..2..2..2....0..0..0..0..1..1..1..1
..0..2..2..2..2..3..3..3....0..2..2..2..2..2..3..3....0..0..0..2..3..3..3..3

Crossrefs

Column 7 of A250877.

Sequence in context: A252621 A234561 A252511 * A165443 A025296 A025315

Adjacent sequences: A250873 A250874 A250875 * A250877 A250878 A250879

Keyword

nonn

Author

R. H. Hardin, Nov 28 2014

Status

approved