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A141505
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Number of n X n binary matrices, symmetric about both diagonal and antidiagonal, with no more than 2 ones in any 2 X 2 subblock.
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0
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1, 2, 3, 9, 21, 113, 469, 4085, 28379, 421721, 4946881, 123415785, 2438547133, 102642272877, 3418605422546, 242398759656743, 13604569959521965, 1625856487869820237, 153782502309772183952, 30970307573051859177121, 4936590429632104565792997, 1675450994355334964940357075
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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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