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A269047
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Number of n X 3 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once.
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1
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24, 102, 594, 3258, 17346, 90450, 464250, 2353338, 11809746, 58773858, 290465706, 1426996746, 6974700162, 33938314674, 164494914138, 794524032090, 3825755303730, 18370501130754, 87990608484618, 420498562000554
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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) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>5.
Empirical g.f.: 6*x*(1 - x)*(1 - 2*x)*(4 - 11*x + 4*x^2) / (1 - 5*x + 2*x^2)^2. - Colin Barker, Jan 18 2019
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EXAMPLE
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Some solutions for n=4:
..2..1..2. .1..2..0. .1..2..2. .1..2..2. .2..1..0. .0..0..0. .0..0..0
..2..1..2. .1..0..1. .1..0..1. .1..2..2. .0..1..2. .0..1..0. .0..0..0
..2..1..0. .0..0..0. .0..0..1. .1..2..1. .2..1..2. .0..1..2. .1..0..1
..2..2..2. .0..0..0. .1..0..0. .0..0..1. .2..2..0. .2..1..2. .1..2..2
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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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