A269037 Number of 3 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.

0, 120, 348, 2166, 9528, 44760, 198816, 877800, 3809856, 16379232, 69769920, 295055136, 1239952512, 5183031744, 21564442752, 89355535680, 368925874944, 1518322209600, 6230763310464, 25503209969088, 104143201935360

Offset

1,2

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - a(n-2) - 28*a(n-3) - 4*a(n-4) + 16*a(n-5) - 4*a(n-6) for n>8.

Empirical g.f.: 6*x^2*(20 - 62*x + 33*x^2 + 40*x^3 - 3*x^4 - 16*x^5 + 4*x^6) / (1 - 3*x - 4*x^2 + 2*x^3)^2. - Colin Barker, Jan 18 2019

Example

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

Crossrefs

Row 3 of A269035.

Sequence in context: A135805 A327912 A118058 * A144524 A052768 A242845

Adjacent sequences: A269034 A269035 A269036 * A269038 A269039 A269040

Keyword

nonn

Author

R. H. Hardin, Feb 18 2016

Status

approved