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A301819
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Number of nX4 0..1 arrays with every element equal to 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.
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1
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2, 8, 25, 68, 177, 457, 1183, 3075, 8018, 20947, 54782, 143348, 375200, 982178, 2571247, 6731462, 17623023, 46137475, 120789253, 316230117, 827900912, 2167472413, 5674516100, 14856075638, 38893710542, 101825055692, 266581456213
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) -13*a(n-2) +13*a(n-3) -6*a(n-4) +a(n-5)
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EXAMPLE
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Some solutions for n=5
..0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..1..1
..1..1..0..0. .0..1..0..0. .0..1..0..1. .0..0..0..0. .0..0..1..1
..0..0..1..1. .1..0..1..1. .1..0..1..0. .1..1..0..1. .0..0..1..0
..1..1..0..1. .0..1..0..0. .0..1..0..1. .1..0..1..1. .1..1..0..1
..0..0..1..1. .1..0..1..1. .1..0..1..1. .0..0..0..0. .0..0..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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