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A139007
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Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.
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2
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1, 2, 5, 25, 205, 2849, 66677, 2633485, 175143651, 19638725775, 3710411382331, 1181447019186469, 633957805831439213, 573281808520220290885, 873645764409736229092874, 2243689725607702437916265557
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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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