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A139006
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Number of n X n symmetric binary matrices containing no more than one 1 in any 2 X 2 sub-block.
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1
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1, 2, 3, 9, 28, 137, 811, 6884, 75303, 1133287, 22573092, 608722751, 21933950111, 1064082678978, 69200610896639, 6047740350081131, 709281636920027844, 111719166691840119209, 23622672695690329752039
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OFFSET
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0,2
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LINKS
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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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