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A067740
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Smallest number k such that sigma(k)/sigma(phi(k)) = n.
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1
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OFFSET
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1,2
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COMMENTS
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The quotient sigma(k)/sigma(phi(k)) is integral for the numbers in A190503. Does a(n) exist for all n?
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LINKS
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FORMULA
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EXAMPLE
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n=6, a(6)=2915640, sigma(2915640)=11793600, phi(2915640)=608256, sigma(608256)=1965600 and 11793600=6*1965600.
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MATHEMATICA
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g[x_] := DivisorSigma[1, x] / DivisorSigma[1, EulerPhi[x]]; m=10; up=200000; a = Table[0, {m}]; Do[ b = g[n]; If[b <= m && IntegerQ[b] && a[[b]] == 0, a[[b]] = n], {n, 1, up} ]; a
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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