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
KEYWORD
nonn
AUTHOR
STATUS
approved