A224404 Number of n X 3 0..1 arrays with rows unimodal and antidiagonals nondecreasing.

7, 28, 100, 358, 1288, 4636, 16684, 60040, 216064, 777544, 2798128, 10069552, 36237040, 130405312, 469286272, 1688808544, 6077472256, 21870844480, 78706050496, 283237457536, 1019279418112, 3668054858368, 13200135512320

Offset: 1

Author

R. H. Hardin, Apr 05 2013

Keywords

• nonn

Comments

Column 3 of A224409.

Examples

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

Links

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

Crossrefs

Cf. A224409.

Formula

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

Empirical g.f.: x*(7 + 2*x^2) / (1 - 4*x + 2*x^2 - 2*x^3). - Colin Barker, Aug 30 2018