A269092 Number of n X 3 0..3 arrays with some element plus some horizontally or vertically adjacent neighbor totalling three exactly once.

24, 1152, 31296, 715320, 15024096, 300056400, 5795398368, 109294975080, 2024660774592, 36988673403168, 668280340085760, 11964667932759960, 212595089870143008, 3753382504394332656, 65903307050002080672

Offset: 1

Author

R. H. Hardin, Feb 19 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A269097.

Formula

Empirical: a(n) = 36*a(n-1) - 378*a(n-2) + 972*a(n-3) - 729*a(n-4) for n>5.

Empirical g.f.: 24*x*(1 + 12*x - 46*x^2 + 33*x^3 + 9*x^4) / (1 - 18*x + 27*x^2)^2. - Colin Barker, Jan 19 2019