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A238906
Number of (n+1) X (1+1) 0..2 arrays with no element equal to all horizontal neighbors or equal to all vertical neighbors, and new values 0..2 introduced in row major order.
1
3, 9, 54, 261, 1341, 6768, 34335, 173925, 881406, 4466169, 22631337, 114678144, 581102091, 2944583217, 14920910982, 75607836957, 383123064069, 1941376545072, 9837421053831, 49848574293549, 252594693861966, 1279957958047665
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) + 6*a(n-2) - 3*a(n-3).
Empirical g.f.: 3*x*(1 - x) / (1 - 4*x - 6*x^2 + 3*x^3). - Colin Barker, Oct 24 2018
EXAMPLE
Some solutions for n=5:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..1..2....2..0....1..2....1..0....2..0....1..0....1..0....1..2....1..0....2..0
..2..0....0..1....0..2....0..1....1..2....2..0....0..1....1..2....0..1....2..1
..0..1....0..1....2..1....1..0....2..1....2..1....0..1....2..0....1..2....1..0
..2..0....1..0....1..0....1..0....0..2....1..2....2..0....1..0....0..1....2..1
..0..1....2..1....0..1....0..1....1..0....2..0....0..2....0..1....2..0....1..2
CROSSREFS
Column 1 of A238912.
Sequence in context: A038496 A175596 A261397 * A363442 A212418 A337039
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 07 2014
STATUS
approved