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