A250875 Number of (n+1) X (6+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.

3680, 18520, 88212, 400496, 1755220, 7500960, 31484612, 130461616, 535577460, 2183825600, 8860495012, 35818848336, 144408578900, 581039033440, 2334380609412, 9368216508656, 37564989535540, 150536411220480

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) = (6608*4^n - 6426*3^n + 1890*2^n + 106)/3.

Empirical g.f.: 4*x*(920 - 4570*x + 7953*x^2 - 4356*x^3) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)). - Colin Barker, Nov 22 2018

Example

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

Crossrefs

Column 6 of A250877.

Sequence in context: A307890 A103608 A204757 * A252311 A263814 A179130

Adjacent sequences: A250872 A250873 A250874 * A250876 A250877 A250878

Keyword

nonn

Author

R. H. Hardin, Nov 28 2014

Status

approved