A015809 Odd numbers k such that phi(k) | sigma_3(k).

1, 3, 15, 35, 87, 95, 105, 135, 147, 209, 215, 285, 297, 315, 357, 455, 551, 609, 627, 635, 645, 783, 899, 957, 1015, 1045, 1107, 1211, 1343, 1349, 1365, 1485, 1505, 1639, 1653, 1905, 1917, 2159, 2261, 2337, 2373, 2639, 2697, 2967, 3045

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[1, 10000, 2], Divisible[DivisorSigma[3, #], EulerPhi[#]] &] (* David Nacin, Mar 04 2012 *)

Prog

(PARI) is(n)=sigma(n, 3)%eulerphi(n)==0

Crossrefs

Sequence in context: A241237 A338351 A145949 * A293995 A015715 A187787

Adjacent sequences: A015806 A015807 A015808 * A015810 A015811 A015812

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Offset changed from 0 to 1 by Vincenzo Librandi, Mar 05 2012

Status

approved