OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..500
MATHEMATICA
Select[Range[900], Mod[DivisorSigma[1, #+13], EulerPhi[#]]==0 &] (* G. C. Greubel, Dec 13 2018 *)
PROG
(PARI) is(n)=!(sigma(n+13)%eulerphi(n)) \\ Charles R Greathouse IV, Sep 25 2012
(Magma) [n: n in [1..900] | DivisorSigma(1, n+13) mod EulerPhi(n) eq 0]; // G. C. Greubel, Dec 13 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Missing a(1)=1 inserted by Sean A. Irvine, Dec 13 2018
STATUS
approved