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A317890
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Number of nX2 0..1 arrays with every element unequal to 2, 3 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.
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3
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0, 1, 1, 2, 5, 16, 45, 123, 340, 946, 2629, 7298, 20260, 56254, 156197, 433691, 1204165, 3343437, 9283266, 25775569, 71567464, 198711505, 551734847, 1531926100, 4253488018, 11810073809, 32791403882, 91047370756, 252798683166
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OFFSET
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1,4
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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) +3*a(n-4) +a(n-5) for n>6
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EXAMPLE
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All solutions for n=5
..0..1. .0..1. .0..1. .0..1. .0..1
..1..0. .1..0. .1..0. .1..0. .1..0
..0..1. .1..0. .1..1. .0..1. .1..0
..0..1. .0..1. .0..1. .1..0. .1..0
..1..0. .1..0. .1..0. .0..1. .0..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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