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A278171
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Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,0) (-1,1) (0,-1) (0,1) (1,-1) or (1,0), with upper left element zero.
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1
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0, 2, 5, 13, 43, 137, 436, 1394, 4458, 14258, 45607, 145888, 466673, 1492823, 4775347, 15275728, 48865129, 156313412, 500027005, 1599523726, 5116675993, 16367605483, 52357919474, 167486425305, 535768092953, 1713855012003, 5482407483581
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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) = 3*a(n-1) + a(n-2) - 3*a(n-4) - 2*a(n-5) - a(n-6) for n>7.
Empirical g.f.: x^2*(1 + x)*(2 - 3*x - x^2 + x^4) / (1 - 3*x - x^2 + 3*x^4 + 2*x^5 + x^6). - Colin Barker, Feb 08 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..0
..0..1. .0..1. .0..1. .1..1. .0..1. .1..1. .0..1. .1..1. .1..0. .1..1
..0..1. .1..1. .1..0. .0..0. .0..0. .1..0. .0..1. .0..1. .1..0. .1..1
..0..0. .0..0. .1..0. .1..1. .1..1. .1..0. .0..1. .0..1. .1..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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