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A191602
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Number of n X n symmetric binary matrices with each 1 adjacent to no more than 3 horizontally, vertically or diagonally neighboring 1s
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1
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2, 8, 52, 686, 16484, 740480, 62224406, 9743390402, 2847964953844, 1553270286186274, 1580697070071238528, 3001650015211411938494, 10635826342196669611219640, 70320933672952732438772180006
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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..1..0..1....0..0..0..1....0..1..1..0....0..0..1..1....1..0..0..0
..1..1..0..1....0..0..0..1....1..0..1..0....0..1..0..1....0..1..0..1
..0..0..0..0....0..0..0..1....1..1..0..0....1..0..0..1....0..0..1..0
..1..1..0..0....1..1..1..0....0..0..0..0....1..1..1..1....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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