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A268887
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Number of 2 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once.
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1
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0, 5, 14, 54, 158, 475, 1340, 3740, 10204, 27521, 73354, 193842, 508346, 1324791, 3433720, 8858104, 22757432, 58253885, 148634502, 378142446, 959527766, 2429034323, 6135877428, 15469187604, 38929330452, 97806402617, 245354321666
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) + 5*a(n-2) - 4*a(n-3) - 11*a(n-4) - 6*a(n-5) - a(n-6).
Empirical g.f.: x^2*(5 + 4*x + x^2) / ((1 + x)^2*(1 - 2*x - x^2)^2). - Colin Barker, Jan 15 2019
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EXAMPLE
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Some solutions for n=4:
..1..0..1..1. .1..1..0..0. .0..0..0..1. .1..0..0..0. .1..0..1..0
..1..0..0..0. .0..1..0..1. .1..1..0..0. .0..1..1..0. .0..1..0..0
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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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