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A297390 Number of n X 3 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 neighboring 1. 1
3, 9, 19, 57, 139, 369, 963, 2489, 6523, 16929, 44147, 114953, 299307, 779697, 2030243, 5287833, 13770971, 35864001, 93402579, 243249193, 633503627, 1649849553, 4296752131, 11190160825, 29142853947, 75897603297, 197662332211 (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) = a(n-1) + 4*a(n-2) + 2*a(n-3) - 4*a(n-4).

Empirical g.f.: x*(1 + 2*x)*(3 - 2*x^2) / (1 - x - 4*x^2 - 2*x^3 + 4*x^4). - Colin Barker, Feb 28 2019

EXAMPLE

Some solutions for n=5:

..0..1..0. .1..1..0. .0..1..1. .0..0..1. .0..1..1. .0..0..0. .1..0..0

..0..0..1. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .1..0..0. .0..1..0

..1..0..0. .0..1..1. .0..1..1. .0..0..0. .1..1..0. .0..1..0. .0..0..0

..0..1..0. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .0..0..0. .0..0..0

..0..0..0. .1..1..0. .0..1..1. .1..0..0. .1..1..0. .1..1..0. .0..1..1

CROSSREFS

Column 3 of A297395.

Sequence in context: A077442 A147455 A146429 * A018316 A146605 A147070

Adjacent sequences:  A297387 A297388 A297389 * A297391 A297392 A297393

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 29 2017

STATUS

approved

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Last modified August 17 17:59 EDT 2022. Contains 356189 sequences. (Running on oeis4.)