A250764 Number of (n+1) X (3+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.

35, 62, 114, 216, 418, 820, 1622, 3224, 6426, 12828, 25630, 51232, 102434, 204836, 409638, 819240, 1638442, 3276844, 6553646, 13107248, 26214450, 52428852, 104857654, 209715256, 419430458, 838860860, 1677721662, 3355443264

Offset: 1

Author

R. H. Hardin, Nov 27 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A250769.

Formula

Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + 2*a(n-3); a(n) = 25*2^(n-1) + 2*n + 8.

Empirical g.f.: x*(35 - 78*x + 41*x^2) / ((1 - x)^2*(1 - 2*x)). - Colin Barker, Nov 18 2018