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A209780
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Half the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having exactly one duplicate clockwise edge difference.
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1
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64, 576, 5074, 44948, 397734, 3520628, 31161462, 275819644, 2441352670, 21609092620, 191268034094, 1692966274828, 14984912401894, 132635602320228, 1173994381706142, 10391348815984084, 91976700981777710, 814111206705377460
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 7*a(n-1) + 22*a(n-2) - 39*a(n-3) - 95*a(n-4) + 30*a(n-6).
Empirical g.f.: 2*x*(32 + 64*x - 183*x^2 - 373*x^3 + 7*x^4 + 120*x^5) / (1 - 7*x - 22*x^2 + 39*x^3 + 95*x^4 - 30*x^6). - Colin Barker, Jul 12 2018
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EXAMPLE
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Some solutions for n=4:
..0..2....2..0....3..3....1..2....1..1....1..1....1..2....3..1....1..0....0..0
..0..1....2..2....0..3....0..2....3..2....2..1....0..2....3..3....0..0....1..0
..0..0....1..1....0..0....2..2....1..1....2..3....0..0....1..1....0..3....2..0
..2..2....0..1....3..3....0..0....1..0....1..3....0..1....3..1....2..1....2..1
..1..2....1..1....3..1....2..2....0..0....1..1....0..1....1..1....0..1....1..1
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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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