A274750 Number of 3 X n 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.

2, 9, 34, 133, 518, 2017, 7858, 30605, 119214, 464345, 1808682, 7044997, 27441030, 106885713, 416331266, 1621654589, 6316517406, 24603508041, 95833284570, 373280851061, 1453968675382, 5663362861249, 22059401583154, 85923718843693

Offset: 1

Author

R. H. Hardin, Jul 04 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 3 of A274749.

Formula

Empirical: a(n) = 2*a(n-1) + 7*a(n-2) + 2*a(n-3) - 2*a(n-4).

Empirical g.f.: x*(2 + 5*x + 2*x^2 - 2*x^3) / ((1 + x)*(1 - 3*x - 4*x^2 + 2*x^3)). - Colin Barker, Jan 30 2019