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

1,1

Comments

Column 3 of A224158.

Links

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

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

Example

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

Crossrefs

Cf. A224158.

Sequence in context: A156928 A117473 A163037 * A361771 A276236 A022572

Adjacent sequences: A224150 A224151 A224152 * A224154 A224155 A224156

Keyword

nonn

Author

R. H. Hardin, Mar 31 2013

Status

approved