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A221236
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Number of n X 2 arrays of occupancy after each element moves to some horizontal, vertical or antidiagonal neighbor, without 2-loops.
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1
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0, 5, 53, 467, 3913, 32299, 265353, 2176758, 17847997, 146319703, 1199485661, 9832876386, 80605364957, 660764392260, 5416629053076, 44402915641056, 363993693602517, 2983844751876537, 24460120087308763, 200512266365651825
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 11*a(n-1) - 23*a(n-2) - a(n-3) + 10*a(n-4) - a(n-6).
Empirical g.f.: x^2*(5 - 2*x - x^2) / ((1 - 3*x + x^2)*(1 - 8*x - 2*x^2 + 3*x^3 + x^4)). - Colin Barker, Aug 04 2018
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EXAMPLE
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Some solutions for n=3:
..1..0....0..0....1..1....0..2....1..1....0..1....1..1....0..2....0..2....0..1
..2..1....2..1....1..3....1..1....1..2....3..2....2..0....2..2....1..3....0..3
..2..0....2..1....0..0....1..1....1..0....0..0....2..0....0..0....0..0....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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