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A062385 Numbers n such that sigma(n)-phi(n) is a perfect cube. +0
2
1, 30, 44, 87, 169, 247, 515, 630, 707, 910, 1067, 1255, 1356, 1691, 2128, 2188, 2291, 2438, 2574, 2627, 2747, 2867, 3668, 3689, 4063, 4295, 5206, 5359, 5999, 6331, 6583, 6835, 7719, 8286, 8968, 8991, 9383 (list; graph; listen)
OFFSET

1,2

EXAMPLE

sigma(30)=phi(30) = 72-8 = 64 = 4^3, so 30 is a term of the sequence.

MATHEMATICA

Select[Range[10^4], IntegerQ[(DivisorSigma[1, # ] - EulerPhi[ # ])^(1/3)] &]

CROSSREFS

Sequence in context: A050776 A090692 A102843 this_sequence A114944 A075290 A004222

Adjacent sequences: A062382 A062383 A062384 this_sequence A062386 A062387 A062388

KEYWORD

nonn

AUTHOR

Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 13 2002

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.


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