A274896 Number of 4 X n 0..2 arrays with no element equal to any value at offset (0,-1) (-1,-1) or (-2,0) and new values introduced in order 0..2.

6, 14, 38, 104, 290, 815, 2291, 6434, 18065, 50729, 142469, 400121, 1123718, 3155882, 8863073, 24891350, 69905726, 196325636, 551367590, 1548479459, 4348802339, 12213324374, 34300315505, 96330172385, 270536931545, 759785117405

Offset: 1

Author

R. H. Hardin, Jul 10 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 4 of A274895.

Formula

Empirical: a(n) = 5*a(n-1) - 9*a(n-2) + 10*a(n-3) - 6*a(n-4) + a(n-5) for n>6.

Empirical g.f.: x*(6 - 16*x + 22*x^2 - 20*x^3 + 8*x^4 - x^5) / ((1 - x)*(1 - 4*x + 5*x^2 - 5*x^3 + x^4)). - Colin Barker, Jan 31 2019