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A269053 Number of 2 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once. 1
9, 42, 102, 360, 1068, 3288, 9864, 29472, 87312, 257184, 753504, 2197632, 6383808, 18478464, 53318784, 153414144, 440293632, 1260710400, 3602253312, 10273007616, 29245172736, 83119822848, 235886217216, 668491456512, 1892026552320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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.: 3*x*(3 + 2*x - 22*x^2 + 8*x^3) / (1 - 2*x - 2*x^2)^2. - Colin Barker, Jan 18 2019

EXAMPLE

Some solutions for n=4:

..1..2..2..2. .2..1..2..1. .0..1..2..1. .1..0..0..1. .1..0..0..1

..2..2..2..1. .2..1..0..0. .0..1..2..1. .0..1..0..0. .0..0..1..0

CROSSREFS

Row 2 of A269052.

Sequence in context: A075233 A062783 A172464 * A027441 A000971 A061927

Adjacent sequences:  A269050 A269051 A269052 * A269054 A269055 A269056

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 18 2016

STATUS

approved

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Last modified June 22 04:06 EDT 2021. Contains 345367 sequences. (Running on oeis4.)