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A191506
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Number of n X n symmetric binary matrices with each 1 adjacent to no more than 1 horizontally or vertically neighboring 1
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1
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2, 5, 25, 195, 2475, 53324, 1872113, 109037035, 10508450377, 1672058437225, 440124911303718, 191498508664286039, 137739615464486164780, 163796811382099494131871, 322006666961136384120723488
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OFFSET
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1,1
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LINKS
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EXAMPLE
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Some solutions for n=4
..1..0..1..0....0..0..0..1....0..1..0..0....0..0..0..1....1..0..0..1
..0..1..0..1....0..0..0..1....1..0..0..0....0..0..1..0....0..1..0..0
..1..0..1..0....0..0..1..0....0..0..1..0....0..1..0..0....0..0..0..1
..0..1..0..1....1..1..0..1....0..0..0..1....1..0..0..1....1..0..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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