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A232508 Number of (n+1) X (1+1) 0..2 arrays with every element next to itself plus and minus one within the range 0..2 horizontally, diagonally or antidiagonally, with no adjacent elements equal. 1
4, 4, 8, 16, 28, 52, 96, 176, 324, 596, 1096, 2016, 3708, 6820, 12544, 23072, 42436, 78052, 143560, 264048, 485660, 893268, 1642976, 3021904, 5558148, 10223028, 18803080, 34584256, 63610364, 116997700, 215192320, 395800384, 727990404 (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) + a(n-2) + a(n-3).

Empirical g.f.: 4*x / (1 - x - x^2 - x^3). - Colin Barker, Oct 05 2018

EXAMPLE

Some solutions for n=7:

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

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

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

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

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

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

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

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

CROSSREFS

Column 1 of A232515.

Sequence in context: A030168 A261212 A112435 * A028610 A019171 A038551

Adjacent sequences:  A232505 A232506 A232507 * A232509 A232510 A232511

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 25 2013

STATUS

approved

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Last modified August 7 22:44 EDT 2020. Contains 336279 sequences. (Running on oeis4.)