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

1,1

Comments

Column 3 of A224409.

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) + 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

Example

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

Crossrefs

Cf. A224409.

Sequence in context: A356038 A241400 A219411 * A370487 A331197 A024207

Adjacent sequences: A224401 A224402 A224403 * A224405 A224406 A224407

Keyword

nonn

Author

R. H. Hardin, Apr 05 2013

Status

approved