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A233013
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Number of n X 3 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally or vertically, top left element zero, and 1 appearing before 2 in row major order.
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1
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5, 74, 1202, 19643, 321125, 5249894, 85827722, 1403151863, 22939385045, 375023830514, 6131065553042, 100233536530883, 1638664887623765, 26789662490893934, 437969972870249162, 7160138624410348703
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 19*a(n-1) - 45*a(n-2) + 27*a(n-3).
Empirical g.f.: x*(5 - 21*x + 21*x^2) / ((1 - x)*(1 - 18*x + 27*x^2)). - Colin Barker, Oct 06 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..1....0..1..3....0..1..1....0..1..1....0..1..3....0..0..1....0..1..0
..1..1..1....0..0..2....2..0..1....2..0..0....1..3..1....0..0..0....1..1..1
..3..1..1....2..2..2....3..2..3....2..2..0....3..1..0....0..0..1....3..3..3
..2..0..0....2..3..2....1..3..3....0..0..2....3..1..1....0..0..1....1..1..3
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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