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A331640
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Number of binary matrices with n columns and any number of distinct nonzero rows with 2 ones in every column.
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3
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1, 0, 6, 120, 6174, 449520, 49686726, 7455901320, 1479839874414, 373573957133280, 117097298726892246, 44596327028174342520, 20287402287658565190654, 10864410524883717498300240, 6765647366010527963979060966, 4847736403559133115838948559720
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OFFSET
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0,3
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LINKS
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EXAMPLE
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The a(2) = 6 matrices are:
[1 1] [1 1] [1 0] [1 0] [0 1] [0 1]
[1 0] [0 1] [1 1] [0 1] [1 1] [1 0]
[0 1] [1 0] [0 1] [1 1] [1 0] [1 1]
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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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