A269284 Number of n X 3 0..3 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling three no more than once.

60, 2124, 62748, 1698732, 43674876, 1085203980, 26317946844, 626778812268, 14718495557052, 341767357185996, 7863372461151900, 179542238849355564, 4073026776304945788, 91888997272241919372, 2063133077083679521116

Offset

1,1

Links

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

Formula

Empirical: a(n) = 42*a(n-1) - 441*a(n-2).

Conjectures from Colin Barker, Jan 21 2019: (Start)

G.f.: 12*x*(5 - 33*x) / (1 - 21*x)^2.

a(n) = 4 * 3^n * 7^(n-2) * (24*n+11).

(End)

Example

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

Crossrefs

Column 3 of A269289.

Sequence in context: A083367 A173123 A004353 * A004364 A371600 A054623

Adjacent sequences: A269281 A269282 A269283 * A269285 A269286 A269287

Keyword

nonn

Author

R. H. Hardin, Feb 21 2016

Status

approved