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A191343
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Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 horizontally, vertically or diagonally neighboring 1
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1
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1, 2, 6, 24, 125, 1055, 11754, 187498, 4372206, 142427556, 6649078485, 443418423639, 42015106781746, 5681500677861845, 1094937801983952063, 300642401916076713227, 117675702292067958725570
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Some solutions for n=4
..0..0..0..0....0..0..0..0....0..0..1..0....0..0..1..0....1..0..0..0
..0..0..0..1....0..0..0..0....0..0..0..1....0..1..0..1....0..1..0..1
..0..0..0..1....0..0..0..0....1..0..0..0....1..0..1..0....0..0..0..1
..0..1..1..0....0..0..0..0....0..1..0..0....0..1..0..0....0..1..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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