A224033 Number of n X 3 0..1 arrays with antidiagonals unimodal and rows and diagonals nondecreasing.

4, 13, 37, 105, 298, 848, 2419, 6908, 19737, 56401, 161181, 460622, 1316360, 3761867, 10750568, 30722673, 87798365, 250907593, 717036338, 2049125344, 5855930115, 16734904820, 47824518777, 136671503209, 390575802373, 1116176041318

Offset: 1

Author

R. H. Hardin, Mar 30 2013

Keywords

• nonn

Comments

Column 3 of A224038.

Examples

			Some solutions for n=3:
..0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..1..1....0..0..0
..0..1..1....1..1..1....0..0..1....0..0..0....0..0..0....1..1..1....0..1..1
..1..1..1....0..1..1....1..1..1....0..0..1....0..1..1....1..1..1....0..1..1
		

Links

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

Crossrefs

Cf. A224038.

Formula

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

Empirical g.f.: x*(1 - x)*(4 + x - 2*x^2 - 2*x^3) / (1 - 4*x + 3*x^2 + x^3 - 2*x^5). - Colin Barker, Aug 26 2018