A274890 Number of n X 3 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.

2, 12, 16, 38, 84, 192, 436, 990, 2253, 5121, 11645, 26483, 60215, 136936, 311381, 708076, 1610154, 3661438, 8326047, 18933223, 43053720, 97903198, 222629593, 506254676, 1151211539, 2617828789, 5952883022, 13536720098, 30782192928

Offset: 1

Author

R. H. Hardin, Jul 10 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A274895.

Formula

Empirical: a(n) = a(n-1) + 4*a(n-2) - 6*a(n-4) - a(n-5) + 4*a(n-6) - a(n-8) for n>10.

Empirical g.f.: x*(2 + 10*x - 4*x^2 - 26*x^3 - 6*x^4 + 30*x^5 + 8*x^6 - 18*x^7 - x^8 + 4*x^9) / ((1 - x)*(1 + x)*(1 - x - 3*x^2 - x^3 + 3*x^4 - x^6)). - Colin Barker, Jan 31 2019