A208023 Number of n X 3 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 1 0 1 vertically.

6, 36, 102, 279, 741, 1995, 5404, 14555, 39180, 105688, 284961, 767907, 2070021, 5580470, 15042195, 40547128, 109300950, 294632265, 794208105, 2140875657, 5770963528, 15556228121, 41933454712, 113036097920, 304700733021

Offset: 1

Author

R. H. Hardin, Feb 22 2012

Keywords

• nonn

Comments

Column 3 of A208028.

Examples

			Some solutions for n=4:
..1..0..0....0..1..1....1..1..1....1..1..1....1..1..0....1..0..0....0..1..0
..0..1..0....0..1..1....1..1..1....0..1..0....0..1..0....0..1..0....1..0..1
..0..1..1....1..0..0....1..1..0....0..1..0....0..1..1....0..1..1....1..0..1
..1..1..1....1..0..0....1..0..0....1..0..1....1..1..1....1..0..0....1..1..1
		

Links

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

Crossrefs

Cf. A208028.

Formula

Empirical: a(n) = a(n-1) + a(n-2) + 8*a(n-3) + 4*a(n-4) + 3*a(n-5) - 5*a(n-6) - a(n-7) + a(n-9) for n>10.

Empirical g.f.: x*(6 + 30*x + 60*x^2 + 93*x^3 + 48*x^4 - 3*x^5 - 50*x^6 - 8*x^7 + 6*x^8 + 9*x^9) / (1 - x - x^2 - 8*x^3 - 4*x^4 - 3*x^5 + 5*x^6 + x^7 - x^9). - Colin Barker, Mar 06 2018