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A140425
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Number of n X n symmetric binary matrices with every 1 adjacent to another 1 horizontally or vertically.
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0
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1, 4, 28, 342, 8170, 388316, 35871274, 6434968504, 2248575047080, 1530856226085764, 2029777404349820818, 5241143888167535563974, 26356732501074298121803368, 258136468277025366420232101764
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OFFSET
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1,2
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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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