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A197617
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Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,3,1,1,1 for x=0,1,2,3,4.
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1
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0, 0, 8, 0, 8, 32, 16, 64, 152, 160, 424, 832, 1216, 2688, 4968, 8384, 16936, 30944, 55440, 107072, 196152, 359776, 679880, 1251456, 2315136, 4330752, 8000840, 14842752, 27638984, 51176864, 95010832, 176575552, 327357272, 607795744
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OFFSET
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1,3
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COMMENTS
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Every 0 is next to 0 0's, every 1 is next to 1 3's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's.
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LINKS
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FORMULA
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Empirical: a(n) = a(n-2) +4*a(n-3) +a(n-4).
Empirical g.f.: 8*x^3 / (1 - x^2 - 4*x^3 - x^4). - Colin Barker, May 14 2018
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EXAMPLE
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All solutions for n=5:
..0..1....1..0....1..2....1..0....1..2....2..1....2..1....0..1
..1..3....3..1....3..1....3..1....3..1....1..3....1..3....1..3
..1..1....1..1....1..1....1..1....1..1....1..1....1..1....1..1
..3..1....1..3....1..3....1..3....1..3....3..1....3..1....3..1
..1..0....0..1....0..1....2..1....2..1....1..0....1..2....1..2
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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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