A269036 Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.

0, 24, 48, 216, 672, 2208, 6912, 21408, 65280, 196992, 589056, 1748352, 5156352, 15124992, 44156928, 128383488, 371908608, 1073879040, 3091820544, 8878479360, 25435250688, 72710922240, 207448571904, 590798364672, 1679765078016

Offset

1,2

Links

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

Formula

Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4).

Empirical g.f.: 24*x^2*(1 - x)^2 / (1 - 2*x - 2*x^2)^2. - Colin Barker, Jan 18 2019

Example

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

Crossrefs

Row 2 of A269035.

Sequence in context: A292834 A362941 A030021 * A268486 A288460 A352699

Adjacent sequences: A269033 A269034 A269035 * A269037 A269038 A269039

Keyword

nonn

Author

R. H. Hardin, Feb 18 2016

Status

approved