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A075865
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phi(n) = sigma(sum of prime factors of n).
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0
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18, 20, 52, 57, 70, 381, 426, 543, 1252, 3027, 4098, 4612, 6807, 257799, 302403, 1583607, 3272727, 52859523
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,1
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EXAMPLE
| phi(52) = 24; sigma(sum of prime factors of 52) = sigma(15) = 24. Hence 52 belongs to the sequence.
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MATHEMATICA
| Select[Range[2, 10^5], DivisorSigma[1, Apply[Plus, Transpose[FactorInteger[ # ]][[1]]]] == EulerPhi[ # ] &]
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CROSSREFS
| Sequence in context: A113541 A181453 A113542 * A066240 A115747 A185099
Adjacent sequences: A075862 A075863 A075864 * A075866 A075867 A075868
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 15 2002
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EXTENSIONS
| a(15)-a(19) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 06 2009
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