A275560 Number of n X 3 0..2 arrays with no element equal to any value at offset (-2,0) (-1,2) or (0,-2) and new values introduced in order 0..2.

3, 36, 126, 504, 1872, 7200, 27360, 104256, 397440, 1513728, 5769216, 21980160, 83755008, 319131648, 1215995904, 4633362432, 17654611968, 67270017024, 256320995328, 976668327936, 3721430827008, 14179888005120, 54030086701056

Offset: 1

Author

R. H. Hardin, Aug 01 2016

Keywords

• nonn

Examples

			Some solutions for n=4:
..0..1..2. .0..0..1. .0..1..2. .0..1..1. .0..0..1. .0..1..2. .0..1..2
..1..0..0. .0..1..2. .1..1..0. .2..2..0. .2..1..1. .0..0..1. .0..1..1
..2..2..1. .1..2..2. .2..2..0. .1..0..2. .2..1..0. .2..2..0. .2..0..1
..0..1..2. .1..0..0. .2..2..1. .0..1..2. .1..0..2. .1..2..0. .2..0..0
		

Links

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

Crossrefs

Column 3 of A275565.

Formula

Empirical: a(n) = 2*a(n-1) + 8*a(n-2) - 16*a(n-4) for n>5.

Empirical g.f.: 3*x*(1 + 10*x + 10*x^2 - 12*x^3 - 32*x^4) / (1 - 2*x - 8*x^2 + 16*x^4). - Colin Barker, Feb 04 2019