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A301902
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Number of n X 3 0..1 arrays with every element equal to 0, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero.
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1
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1, 2, 3, 7, 16, 43, 117, 330, 935, 2667, 7616, 21775, 62273, 178130, 509563, 1457727, 4170224, 11930147, 34129757, 97638522, 279324735, 799093699, 2286051744, 6539949991, 18709526921, 53524323778, 153122698291, 438054310967
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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) -4*a(n-3).
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EXAMPLE
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Some solutions for n=5
..0..1..1. .0..1..0. .0..1..1. .0..1..1. .0..1..1. .0..1..1. .0..1..0
..1..1..0. .0..1..1. .1..1..0. .1..1..1. .1..1..0. .1..1..1. .0..1..0
..1..1..1. .1..1..1. .1..1..0. .0..1..1. .0..1..0. .0..1..1. .0..1..0
..0..1..1. .0..1..1. .1..1..1. .0..1..1. .0..1..1. .1..1..0. .0..1..0
..1..1..0. .1..1..0. .1..1..0. .1..1..0. .1..1..0. .0..1..0. .0..1..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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