A275184 Number of 4 X n 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,0) or (-1,1) and new values introduced in order 0..2.

4, 12, 41, 141, 482, 1651, 5653, 19356, 66277, 226937, 777050, 2660679, 9110369, 31194604, 106812721, 365734965, 1252304626, 4287987275, 14682397949, 50273658876, 172140871373, 589423572097, 2018231606314, 6910580115135

Offset: 1

Author

R. H. Hardin, Jul 19 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 4 of A275183.

Formula

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

Empirical g.f.: x*(4 + 4*x + x^2 - x^3) / (1 - 2*x - 4*x^2 - 3*x^3). - Colin Barker, Feb 01 2019