A250785 Number of (3+1) X (n+1) 0..1 arrays with nondecreasing 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.

36, 96, 230, 534, 1194, 2604, 5568, 11732, 24442, 50482, 103566, 211360, 429580, 870280, 1758574, 3546318, 7139858, 14356148, 28835992, 57872156, 116068226, 232660586, 466169270, 933710824, 1869642084, 3742876944, 7491567158

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 2*x*(18 - 42*x + 19*x^2 + 22*x^3 - 16*x^4) / ((1 - x)^2*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Nov 19 2018

Example

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

Crossrefs

Row 3 of A250783.

Sequence in context: A242238 A200866 A324297 * A057392 A287613 A118632

Adjacent sequences: A250782 A250783 A250784 * A250786 A250787 A250788

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved