A067232 Numbers n such that phi(3n-1) = sigma(n).

1, 3, 5, 7, 35, 39, 47, 51, 145, 210, 215, 287, 321, 355, 385, 532, 572, 635, 702, 1248, 1357, 1566, 1577, 1720, 1837, 2241, 2619, 2635, 2910, 3243, 4117, 4290, 4311, 5010, 5346, 5495, 5605, 6557, 7565, 7637, 7683, 9342, 9741, 9798, 10792, 11679, 13039

Offset

1,2

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[14000], EulerPhi[3#-1]==DivisorSigma[1, #]&] (* Harvey P. Dale, Feb 03 2015 *)

Prog

(PARI) isok(n) = eulerphi(3*n-1) == sigma(n); \\ Michel Marcus, Nov 21 2013

Crossrefs

Cf. A000010, A000203, A067233.

Sequence in context: A137864 A256154 A069969 * A327413 A106115 A154544

Adjacent sequences: A067229 A067230 A067231 * A067233 A067234 A067235

Keyword

nonn

Author

Benoit Cloitre, Feb 20 2002

Status

approved