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A297309
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Number of n X 3 0..1 arrays with every 1 horizontally or antidiagonally adjacent to 1 or 2 neighboring 1s.
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1
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4, 23, 117, 609, 3159, 16389, 85041, 441225, 2289339, 11878281, 61631001, 319774761, 1659164103, 8608637997, 44666257401, 231752633913, 1202457662523, 6238998904833, 32371291359585, 167959719216009, 871465613342823
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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) = 3*a(n-1) + 11*a(n-2) + 3*a(n-3) - 6*a(n-4).
Empirical g.f.: x*(4 + 11*x + 4*x^2 - 7*x^3) / (1 - 3*x - 11*x^2 - 3*x^3 + 6*x^4). - Colin Barker, Feb 26 2019
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EXAMPLE
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Some solutions for n=5:
..1..1..1. .0..1..0. .1..1..0. .0..1..0. .1..1..0. .0..0..0. .1..1..0
..0..1..0. .1..0..0. .1..1..1. .1..0..1. .1..1..0. .0..0..0. .1..1..1
..1..0..0. .1..1..1. .0..0..0. .0..1..0. .1..0..1. .0..0..0. .0..0..0
..0..0..1. .0..1..0. .1..1..1. .1..1..0. .0..1..0. .1..1..0. .0..1..0
..1..1..0. .0..1..1. .0..1..1. .0..0..0. .0..1..1. .1..1..1. .1..1..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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