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A280674
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Number of 2 X n 0..2 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors and with new values introduced in order 0 sequentially upwards.
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1
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2, 11, 59, 338, 1917, 10893, 61880, 351541, 1997095, 11345458, 64453321, 366158041, 2080136592, 11817214849, 67133363931, 381383313234, 2166631062437, 12308588230773, 69924846394792, 397241669934877, 2256722073320511
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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) = 5*a(n-1) + 6*a(n-2) - 11*a(n-3) - 7*a(n-4) + 4*a(n-5) for n>6.
Empirical g.f.: x*(1 - x)*(2 + 3*x - x^2)*(1 - 2*x^2) / ((1 + x)*(1 - 6*x + 11*x^3 - 4*x^4)). - Colin Barker, Feb 14 2019
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EXAMPLE
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Some solutions for n=4:
..0..0..1..0. .0..1..0..2. .0..1..1..2. .0..1..0..1. .0..0..1..2
..2..0..2..1. .1..2..0..2. .0..2..0..2. .1..0..2..2. .1..0..0..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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