A231390 Number of (n+1) X (2+1) 0..2 arrays with no element unequal to a strict majority of its horizontal, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order.

7, 8, 15, 20, 31, 52, 95, 180, 351, 692, 1375, 2740, 5471, 10932, 21855, 43700, 87391, 174772, 349535, 699060, 1398111, 2796212, 5592415, 11184820, 22369631, 44739252, 89478495, 178956980, 357913951, 715827892, 1431655775, 2863311540, 5726623071

Offset: 1

Author

R. H. Hardin, Nov 08 2013

Keywords

• nonn

Examples

			Some solutions for n=5:
..0..0..0....0..1..1....0..0..0....0..0..0....0..1..0....0..0..0....0..0..0
..1..1..1....1..0..1....0..0..0....1..1..1....1..0..1....0..0..0....0..0..0
..1..1..1....0..1..0....0..0..0....1..1..1....0..1..0....1..1..1....0..0..0
..2..2..2....1..0..1....0..0..0....1..1..1....1..0..1....1..1..1....1..1..1
..2..2..2....0..1..0....0..0..0....0..0..0....0..1..0....1..1..1....1..1..1
..1..1..1....0..0..1....1..1..1....0..0..0....1..0..1....0..0..0....0..0..0
		

Links

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

Crossrefs

Column 2 of A231396.

Formula

Empirical: a(n) = 2*a(n-1) + a(n-2) - 2*a(n-3) for n>5.

Empirical g.f.: x*(7 - 6*x - 8*x^2 - 4*x^3 - 8*x^4) / ((1 - x)*(1 + x)*(1 - 2*x)). - Colin Barker, Sep 28 2018