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A221397 Number of n X 3 arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2. 1
0, 6, 30, 144, 672, 3108, 14328, 65976, 303672, 1397520, 6431136, 29594352, 136184256, 626677152, 2883768672, 13270180608, 61065117312, 281002082880, 1293081432192, 5950345861248, 27381582408576, 126001256419584 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 3 of A221400.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..41

FORMULA

Empirical: a(n) = 6*a(n-1) - 6*a(n-2)  -2*a(n-3).

Empirical g.f.: 6*x^2*(1 - x) / (1 - 6*x + 6*x^2 + 2*x^3). - Colin Barker, Aug 05 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A221400.

Sequence in context: A307321 A026749 A003279 * A082134 A030192 A026376

Adjacent sequences:  A221394 A221395 A221396 * A221398 A221399 A221400

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 15 2013

STATUS

approved

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Last modified July 17 09:09 EDT 2019. Contains 325099 sequences. (Running on oeis4.)