A250792 Number of (n+1) X (3+1) 0..1 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.

54, 162, 482, 1430, 4258, 12706, 37986, 113694, 340562, 1020650, 3059890, 9175558, 27518466, 82538994, 247584194, 742687022, 2227929970, 6683527738, 20050058898, 60149128086, 180445287074, 541331666882, 1623986612002, 4871943058750

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 10*a(n-2) + 11*a(n-4) - 6*a(n-5).

Conjectures from Colin Barker, Nov 20 2018: (Start)

G.f.: 2*x*(27 - 81*x + 25*x^2 + 79*x^3 - 48*x^4) / ((1 - x)^2*(1 + x)*(1 - 2*x)*(1 - 3*x)).

a(n) = -3 - (-1)^n/4 + 2^(1+n) + (23*3^(1+n))/4 + n.

(End)

Example

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

Crossrefs

Column 3 of A250797.

Sequence in context: A304172 A044386 A044767 * A044980 A248598 A157428

Adjacent sequences: A250789 A250790 A250791 * A250793 A250794 A250795

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved