A250730 Number of (1+1)X(n+1) 0..1 arrays with nondecreasing x(i,j)+x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

9, 22, 50, 114, 257, 579, 1302, 2927, 6578, 14782, 33216, 74637, 167709, 376840, 846753, 1902638, 4275190, 9606266, 21585085, 48501247, 108981314, 244878791, 550237650, 1236372778, 2778104416, 6242343961, 14026419561, 31517078668

Offset: 1

Author

R. H. Hardin, Nov 27 2014

Keywords

• nonn

Comments

Row 1 of A250729

Examples

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

Links

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

Formula

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

Empirical: G.f. x*( -9+5*x+7*x^2-4*x^3 ) / ( (x-1)*(x^3-x^2-2*x+1) ). - R. J. Mathar, Nov 27 2014