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A091911
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a(n) = smallest number m such that m*tau(m)/sigma(m) = n, or 0 if no such m exists.
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2
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1, 6, 28, 0, 140, 270, 8128, 672, 1638, 6200, 2970, 0, 105664, 18620, 8190, 0, 27846, 0, 117800, 0, 55860, 0, 0, 30240, 173600, 242060, 167400, 0, 237510, 0, 2305843008139952128, 0, 0, 0, 2229500, 0, 4358600, 0, 726180, 0, 2290260, 1089270
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OFFSET
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1,2
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COMMENTS
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LINKS
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MATHEMATICA
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f[n_] := (n*DivisorSigma[0, n]/DivisorSigma[1, n]); a = Table[0, {50}]; Do[ b = f[n]; If[ IntegerQ[b] && b < 51 && a[[b]] == 0, a[[b]] = n], {n, 1, 10 ^7}]; a
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CROSSREFS
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The zeros occur at the complement of A090240.
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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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