A066930 Numbers k such that phi(sigma(k)) divides sigma(phi(k)).

1, 7, 9, 29, 71, 97, 109, 121, 139, 142, 175, 183, 194, 215, 225, 242, 244, 261, 278, 311, 344, 349, 355, 430, 497, 509, 516, 533, 556, 571, 605, 622, 631, 647, 673, 709, 729, 791, 817, 859, 911, 923, 1021, 1066, 1112, 1119, 1142, 1207, 1243, 1262, 1277

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[1300], Divisible[DivisorSigma[1, EulerPhi[#]], EulerPhi[ DivisorSigma[ 1, #]]]&] (* Harvey P. Dale, Dec 15 2021 *)

Prog

(PARI) isok(k) = { sigma(eulerphi(k)) % eulerphi(sigma(k)) == 0 } \\ Harry J. Smith, Apr 08 2010

Crossrefs

Cf. A033632.

Sequence in context: A030404 A242505 A263826 * A247192 A154260 A309199

Adjacent sequences: A066927 A066928 A066929 * A066931 A066932 A066933

Keyword

nonn

Author

Benoit Cloitre, Jan 26 2002

Status

approved