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A217340 Number of n X 2 arrays of occupancy after each element moves to some horizontal or vertical neighbor but without 2-loops 6
0, 1, 7, 38, 190, 918, 4367, 20623, 97052, 455960, 2140404, 10043697, 47120343, 221046178, 1036902766, 4863888050, 22815211759, 107019570351, 501996648392, 2354712588592, 11045229346424, 51809744028497, 243023401329015 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Column 2 of A217346.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 7*a(n-1) -11*a(n-2) +a(n-3) -a(n-4).

Empirical g.f.: x^2 / (1 - 7*x + 11*x^2 - x^3 + x^4). - Colin Barker, Feb 18 2018

EXAMPLE

All solutions for n=3:

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

..2..2....1..2....2..1....2..2....2..1....1..2....1..1

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

CROSSREFS

Sequence in context: A099453 A292535 A026763 * A037696 A026895 A037605

Adjacent sequences:  A217337 A217338 A217339 * A217341 A217342 A217343

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 01 2012

STATUS

approved

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Last modified July 25 10:18 EDT 2021. Contains 346289 sequences. (Running on oeis4.)