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A281394
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Number of n X 2 0..1 arrays with no element equal to more than two of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.
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1
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0, 0, 6, 36, 160, 676, 2692, 10352, 38868, 143276, 520736, 1871380, 6663484, 23545568, 82661076, 288590204, 1002706896, 3469289876, 11959062188, 41088781264, 140757051348, 480912678028, 1639160372000, 5574818816340
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OFFSET
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1,3
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 6*a(n-3) - 5*a(n-4) + 12*a(n-5) + 4*a(n-6) - 4*a(n-8).
Empirical g.f.: 2*x^3*(1 + x - x^2)*(3 - 3*x - x^2) / (1 - 3*x - x^2 + 2*x^4)^2. - Colin Barker, Feb 18 2019
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EXAMPLE
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Some solutions for n=4:
..0..1. .0..0. .0..0. .0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..1
..1..1. .0..1. .0..0. .0..1. .1..1. .0..1. .0..0. .0..1. .0..0. .0..1
..0..1. .1..1. .1..0. .1..1. .0..1. .1..1. .1..0. .0..0. .0..1. .0..0
..1..0. .0..1. .0..1. .0..1. .1..1. .1..1. .0..0. .0..1. .1..1. .0..0
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CROSSREFS
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Column 2 of A281400.
Sequence in context: A223946 A223919 A263952 * A225380 A225012 A228458
Adjacent sequences: A281391 A281392 A281393 * A281395 A281396 A281397
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Jan 21 2017
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STATUS
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approved
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