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A230800 Number of n X 2 0..3 arrays x(i,j) with each element horizontally or vertically next to at least one element with value (x(i,j)+1) mod 4 and at least one element with value (x(i,j)-1) mod 4, and upper left element zero. 2
0, 2, 2, 16, 34, 154, 432, 1618, 5058, 17664, 57586, 195866, 648928, 2185122, 7284482, 24435056, 81651394, 273490714, 914714512, 3062116338, 10245066178, 34289257824, 114738331026, 383986878106, 1284957453248, 4300144520002 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A230805.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + 6*a(n-2) - 5*a(n-3).

Empirical g.f.: 2*x^2*(1 - x) / (1 - 2*x - 6*x^2 + 5*x^3). - Colin Barker, Mar 17 2018

EXAMPLE

Some solutions for n=4:

..0..3....0..1....0..1....0..3....0..1....0..1....0..1....0..3....0..3....0..3

..1..2....3..2....3..2....1..2....3..2....3..2....3..2....1..2....1..2....1..2

..3..0....2..1....3..0....2..3....1..2....1..0....0..1....0..3....1..2....3..2

..2..1....3..0....2..1....1..0....0..3....2..3....3..2....1..2....0..3....0..1

CROSSREFS

Cf. A230805.

Sequence in context: A113123 A303567 A177832 * A076615 A098777 A127226

Adjacent sequences:  A230797 A230798 A230799 * A230801 A230802 A230803

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 30 2013

STATUS

approved

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Last modified April 12 17:48 EDT 2021. Contains 342929 sequences. (Running on oeis4.)