A279971 Number of n X 2 0..1 arrays with no element equal to a strict majority of its horizontal and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.

1, 3, 9, 31, 108, 366, 1205, 3873, 12207, 37859, 115842, 350412, 1049545, 3116655, 9185349, 26890375, 78253896, 226510362, 652483133, 1871302893, 5345409483, 15213423371, 43153001406, 122024489304, 344061371665, 967537410459

Offset: 1

Author

R. H. Hardin, Dec 24 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A279977.

Formula

Empirical: a(n) = 9*a(n-1) - 30*a(n-2) + 45*a(n-3) - 30*a(n-4) + 9*a(n-5) -a(n-6).

Empirical g.f.: x*(1 - 2*x)*(1 - 4*x + 4*x^2 + 3*x^3) / (1 - 3*x + x^2)^3. - Colin Barker, Feb 12 2019