A275560 Number of n X 3 0..2 arrays with no element equal to any value at offset (-2,0) (-1,2) or (0,-2) and new values introduced in order 0..2.

3, 36, 126, 504, 1872, 7200, 27360, 104256, 397440, 1513728, 5769216, 21980160, 83755008, 319131648, 1215995904, 4633362432, 17654611968, 67270017024, 256320995328, 976668327936, 3721430827008, 14179888005120, 54030086701056

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 8*a(n-2) - 16*a(n-4) for n>5.

Empirical g.f.: 3*x*(1 + 10*x + 10*x^2 - 12*x^3 - 32*x^4) / (1 - 2*x - 8*x^2 + 16*x^4). - Colin Barker, Feb 04 2019

Example

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

Crossrefs

Column 3 of A275565.

Sequence in context: A158077 A324157 A268591 * A213848 A006428 A068619

Adjacent sequences: A275557 A275558 A275559 * A275561 A275562 A275563

Keyword

nonn

Author

R. H. Hardin, Aug 01 2016

Status

approved