A250987 Number of (n+1) X (1+1) 0..2 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.

40, 158, 612, 2323, 8726, 32554, 120930, 447985, 1656600, 6118822, 22583412, 83309947, 307230262, 1132763986, 4175945922, 15393274457, 56738968328, 209129360814, 770792626564, 2840879847779, 10470404185174, 38589657774202

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 8*a(n-3) + 7*a(n-4) + 6*a(n-5) + a(n-6).

Empirical g.f.: x*(40 - 82*x - 56*x^2 + 77*x^3 + 56*x^4 + 9*x^5) / ((1 - 2*x - x^2)*(1 - 4*x + 4*x^3 + x^4)). - Colin Barker, Nov 24 2018

Example

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

Crossrefs

Column 1 of A250994.

Sequence in context: A135848 A089548 A282090 * A300963 A146762 A190073

Adjacent sequences: A250984 A250985 A250986 * A250988 A250989 A250990

Keyword

nonn

Author

R. H. Hardin, Nov 29 2014

Status

approved