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 A112728 Numbers n such that geometric mean of phi(n), n and sigma(n) is an integer. 0
 1, 37044, 1222452, 193637687880 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS It is interesting that a(2) divides a(3). There is no further term up to 6*10^8. a(5) > 4*10^11. - Giovanni Resta, Jul 13 2013 LINKS EXAMPLE (phi(1222452)*1222452*sigma(1222452))^(1/3)=1164240 is an integer, so 1222452 is a term of the sequence. MATHEMATICA Do[If[IntegerQ[(n*DivisorSigma[1, n] EulerPhi[n])^(1/3)], Print[n]], {n, 600000000}] CROSSREFS Cf. A011257. Sequence in context: A057881 A206051 A279862 * A250882 A219363 A254564 Adjacent sequences:  A112725 A112726 A112727 * A112729 A112730 A112731 KEYWORD more,nonn AUTHOR Farideh Firoozbakht, Dec 01 2005 EXTENSIONS a(4) from Giovanni Resta, Jul 13 2013 STATUS approved

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Last modified August 6 08:22 EDT 2020. Contains 336228 sequences. (Running on oeis4.)