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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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6
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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, 563462139240, 1140028049160
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OFFSET
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1,2
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COMMENTS
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a(34) <= 9015394227840, a(35) <= 1255683068640. - Giovanni Resta, May 08 2017
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LINKS
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FORMULA
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MATHEMATICA
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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
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Compare A087979, which has a slightly different definition.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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