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A317760
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Number of nX4 0..1 arrays with every element unequal to 0, 1 or 2 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.
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1
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8, 20, 28, 43, 72, 127, 232, 432, 813, 1539, 2922, 5557, 10577, 20141, 38362, 73076, 139212, 265212, 505263, 962600, 1833903, 3493880, 6656412, 12681561, 24160471, 46029702, 87694221, 167072053, 318300013, 606414406, 1155320200, 2201076948
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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-2) -2*a(n-3) -a(n-4) +a(n-5) for n>6
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EXAMPLE
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Some solutions for n=5
..0..1..1..0. .0..0..0..1. .0..0..0..0. .0..0..0..0. .0..1..1..1
..1..1..0..0. .0..0..1..1. .0..0..0..1. .0..0..0..0. .1..1..1..1
..1..0..0..1. .0..1..1..0. .0..0..1..1. .0..0..0..0. .1..1..1..1
..0..0..1..1. .1..1..0..0. .0..1..1..1. .0..0..0..1. .0..0..0..0
..0..1..1..1. .1..0..0..0. .1..1..1..0. .0..0..1..1. .0..0..0..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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