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A269036 Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A073763 A292834 A030021 * A268486 A288460 A105844

Adjacent sequences:  A269033 A269034 A269035 * A269037 A269038 A269039

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 18 2016

STATUS

approved

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Last modified July 6 08:51 EDT 2020. Contains 335476 sequences. (Running on oeis4.)