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Search: id:A067740
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| A067740 |
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a(n) is the smallest number m such that Sigma[m]/Sigma[Phi[m]]=n. |
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+0
1
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OFFSET
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1,2
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FORMULA
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a(n)=Min{x; A000203(x)/A000203[A000010(x)]=n}
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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+1 && a[[b]] == 0, a[[b]] = n], {n, 1, up} ]; a
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CROSSREFS
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Cf. A000203, A000010, A067385.
Sequence in context: A040194 A107834 A070701 this_sequence A037923 A040195 A040189
Adjacent sequences: A067737 A067738 A067739 this_sequence A067741 A067742 A067743
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KEYWORD
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more,nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jan 29 2002
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