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A181345
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Number of n X n matrices over {0,1} with rows and columns summing to 3, rows and columns sorted (>) by value.
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3
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0, 0, 0, 1, 2, 12, 87, 662, 5611, 51141, 509277, 5504398, 64122940, 800741192, 10673478573, 151323048909
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OFFSET
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1,5
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LINKS
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EXAMPLE
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n=4: {1110,1101,1011,0111} is the only matrix where each row (column) - read as a binary number - is larger than the previous one, so a(4)=1.
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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Michael Steyer (m.steyer(AT)osram.de), Oct 18 2010
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EXTENSIONS
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STATUS
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approved
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