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A088830
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a(n)= Min{x : sigma[x]=n.phi[x], x is not a prime}, the least nonprime solutions to sigma[x]=n.phi[x]; special balanced numbers.
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5
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1, 35, 15, 14, 56, 6, 12, 42, 30, 168, 2580, 210, 630, 420, 840, 20790, 416640, 9240, 291060, 83160, 120120, 5165160, 1719277560, 43825320, 26860680, 277560360, 1304863560, 569729160, 587133466920, 16522145640, 33044291280
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| For n > 3, a(n) = A055234(n). - David Wasserman (wasserma(AT)spawar.navy.mil), Aug 18 2005
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MATHEMATICA
| ds[x_, de_] := DivisorSigma[1, x]-de*EulerPhi[x] a[n_] := Block[{m=1, s=ds[m, n]}, While[(s !=0||PrimeQ[m])&&!Greater[m, 100000], m++ ]; m]; Table[a[n], {n, 22}]
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CROSSREFS
| Compare A087979, which has a slightly different definition. Cf. A074891, A000203, A000010, A087979, A020492.
Cf. A055234.
Sequence in context: A037934 A034086 A051050 * A033355 A174027 A022991
Adjacent sequences: A088827 A088828 A088829 * A088831 A088832 A088833
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Nov 03 2003
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EXTENSIONS
| More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Aug 18 2005
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