A015817 Numbers n such that phi(n + 1) | sigma(n) for n congruent to 1 (mod 3).

1, 7, 28, 31, 55, 94, 127, 265, 322, 385, 406, 649, 1504, 1624, 1990, 2488, 3115, 3154, 4402, 5269, 6265, 6460, 7258, 7384, 7579, 8191, 8455, 8995, 9229, 9799, 11815, 12466, 13114, 13243, 14146, 15385, 16309, 16849, 17731, 20995, 23359

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..100

Mathematica

Select[Range[1, 100000, 3], Divisible[DivisorSigma[1, #], EulerPhi[1 + #]] &] (* David Nacin, Mar 01 2012 *)

Prog

(PARI) is(n)=n%3==1 && sigma(n)%(eulerphi(n)+1)==0 \\ Charles R Greathouse IV, Sep 25 2012

Crossrefs

Sequence in context: A184331 A267432 A155712 * A103253 A321777 A269451

Adjacent sequences: A015814 A015815 A015816 * A015818 A015819 A015820

Keyword

nonn

Author

Robert G. Wilson v

Status

approved