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A301657
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Number of nX3 0..1 arrays with every element equal to 0, 1 or 4 horizontally or vertically adjacent elements, with upper left element zero.
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1
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3, 4, 6, 9, 15, 26, 46, 83, 151, 276, 506, 929, 1707, 3138, 5770, 10611, 19515, 35892, 66014, 121417, 223319, 410746, 755478, 1389539, 2555759, 4700772, 8646066, 15902593, 29249427, 53798082, 98950098, 181997603, 334745779, 615693476
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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) = 2*a(n-1) -a(n-4)
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EXAMPLE
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Some solutions for n=5
..0..0..1. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..0. .0..1..1
..1..1..0. .1..1..1. .0..1..0. .1..0..1. .1..1..1. .1..0..1. .1..0..0
..0..0..1. .0..1..0. .1..0..1. .1..0..1. .0..1..0. .0..0..0. .0..1..1
..1..1..0. .1..0..1. .1..0..1. .0..1..0. .1..0..1. .1..0..1. .1..0..0
..0..0..1. .0..1..0. .0..1..0. .0..1..0. .1..0..1. .0..1..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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