A075865 Numbers n such that phi(n) = sigma(sum of distinct prime factors of n).

18, 20, 52, 57, 70, 381, 426, 543, 1252, 3027, 4098, 4612, 6807, 257799, 302403, 1583607, 3272727, 52859523, 20402085927

Offset

1,1

Links

Table of n, a(n) for n=1..19.

Example

phi(52) = 24; sigma(sum of prime factors of 52) = sigma(15) = 24. Hence 52 belongs to the sequence.

Mathematica

Select[Range[2, 10^5], DivisorSigma[1, Apply[Plus, Transpose[FactorInteger[ # ]][[1]]]] == EulerPhi[ # ] &]

Crossrefs

Cf. A000010, A000203, A008472.

Sequence in context: A113541 A181453 A113542 * A250113 A182226 A066240

Adjacent sequences: A075862 A075863 A075864 * A075866 A075867 A075868

Keyword

nonn

Author

Joseph L. Pe, Oct 15 2002

Extensions

a(14)-a(18) from Donovan Johnson, Jun 06 2009

Name clarified, offset corrected, term a(19) added, Donovan Johnson, Mar 01 2014

Status

approved