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A209979
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Number of unimodular 2 X 2 matrices having all elements in {1,2,...,n}.
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3
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0, 0, 4, 16, 28, 56, 68, 112, 140, 184, 212, 288, 316, 408, 452, 512, 572, 696, 740, 880, 940, 1032, 1108, 1280, 1340, 1496, 1588, 1728, 1820, 2040, 2100, 2336, 2460, 2616, 2740, 2928, 3020, 3304, 3444, 3632, 3756, 4072, 4164, 4496, 4652, 4840
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OFFSET
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0,3
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COMMENTS
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Equivalently, the number of 2 X 2 matrices having all elements in {1,2,...,n} and having an inverse whose elements are all integers.
See A210000 for a guide to related sequences.
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LINKS
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FORMULA
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MATHEMATICA
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(See the Mathematica section at A210000.)
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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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