A269209 Number of n X 3 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three exactly once.

24, 768, 18048, 361728, 6712704, 118872576, 2039727744, 34214296320, 564168820608, 9179147971584, 147751571802240, 2357407757843712, 37337046775523712, 587670598254177792, 9200252201653201536

Offset: 1

Author

R. H. Hardin, Feb 20 2016

Keywords

• nonn

Examples

			Some solutions for n=3:
..0..0..0. .2..0..0. .3..2..3. .1..3..1. .2..0..0. .2..3..3. .2..3..3
..0..0..2. .2..2..2. .2..2..3. .1..1..1. .1..2..2. .1..3..3. .3..1..3
..1..2..2. .0..3..2. .3..3..0. .3..3..0. .3..3..2. .2..0..2. .0..1..0
		

Links

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

Crossrefs

Column 3 of A269214.

Formula

Empirical: a(n) = 30*a(n-1) - 237*a(n-2) + 180*a(n-3) - 36*a(n-4) for n>5.

Empirical g.f.: 24*x*(1 + 2*x + 29*x^2 - 84*x^3 + 36*x^4) / (1 - 15*x + 6*x^2)^2. - Colin Barker, Jan 20 2019