A224153 Number of n X 3 0..1 arrays with diagonals and rows unimodal and antidiagonals nondecreasing.

7, 28, 89, 281, 900, 2935, 9681, 32020, 105937, 350311, 1157860, 3826287, 12643725, 41780500, 138063433, 456233915, 1507641652, 4982061047, 16463412165, 54403960596, 179779885769, 594089193379, 1963189403076, 6487431018743

Offset: 1

Author

R. H. Hardin, Mar 31 2013

Keywords

• nonn

Comments

Column 3 of A224158.

Examples

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

Links

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

Crossrefs

Cf. A224158.

Formula

Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - a(n-3) - 4*a(n-4) + 14*a(n-5) - 2*a(n-6) - 2*a(n-9).

Empirical g.f.: x*(7 - 9*x^2 - 12*x^3 + 10*x^4 - 2*x^8) / (1 - 4*x + 2*x^2 + x^3 + 4*x^4 - 14*x^5 + 2*x^6 + 2*x^9). - Colin Barker, Aug 28 2018