A274745 Number of n X 4 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2.

4, 22, 133, 813, 4967, 30349, 185435, 1133025, 6922887, 42299477, 258453699, 1579175897, 9648910127, 58955729261, 360224933899, 2201007512401, 13448358549783, 82170708943301, 502070597184787, 3067697574952457

Offset: 1

Author

R. H. Hardin, Jul 04 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 4 of A274749.

Formula

Empirical: a(n) = 6*a(n-1) + a(n-2) - 2*a(n-3) for n>4.

Empirical g.f.: x*(1 - x)*(4 + 2*x - x^2) / (1 - 6*x - x^2 + 2*x^3). - Colin Barker, Jan 30 2019