A276293 Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,1) or (0,-1) and new values introduced in order 0..2.

1, 4, 11, 31, 88, 250, 710, 2016, 5724, 16252, 46144, 131016, 371992, 1056192, 2998832, 8514544, 24175232, 68640416, 194889824, 553348096, 1571113920, 4460842944, 12665612288, 35961305216, 102104457600, 289903834112

Offset: 1

Author

R. H. Hardin, Aug 28 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A276299.

Formula

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

Empirical g.f.: x*(1 - x^2 + x^3) / (1 - 4*x + 4*x^2 - 2*x^3). - Colin Barker, Feb 05 2019