A269104 Number of n X 3 0..3 arrays with some element plus some horizontally or vertically adjacent neighbor totalling three no more than once.

60, 1740, 40908, 872460, 17593092, 342055548, 6482020140, 120520189980, 2208175854948, 39988864047276, 717328864510092, 12766536225007020, 225704408971133124, 3967699804321484124, 69407066832964073964

Offset

1,1

Links

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

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.: 12*x*(5 - 35*x + 79*x^2 - 69*x^3 + 18*x^4) / (1 - 18*x + 27*x^2)^2. - Colin Barker, Jan 19 2019

Example

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

Crossrefs

Column 3 of A269109.

Sequence in context: A160349 A281373 A053528 * A017776 A035725 A035800

Adjacent sequences: A269101 A269102 A269103 * A269105 A269106 A269107

Keyword

nonn

Author

R. H. Hardin, Feb 19 2016

Status

approved