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%I #18 Jan 10 2019 10:23:12
%S 5,7,10,31,47,79,127,145,161,223,238,239,355,367,371,376,418,455,463,
%T 479,748,863,1039,1045,1087,1103,1118,1327,1423,1439,1567,1583,1823,
%U 1886,1999,2065,2108,2143,2201,2207,2239,2447,2461,2687,2767,2840,2927,2975
%N Numbers n such that phi(n + 9) | sigma(n) for n not congruent to 0 (mod 3).
%C Includes primes p such that (p+9)/8 is prime. Thus Dickson's conjecture implies the sequence is infinite. - _Robert Israel_, Jan 10 2019
%H Robert Israel, <a href="/A015849/b015849.txt">Table of n, a(n) for n = 1..10000</a>
%p select(n -> (numtheory:-sigma(n)/numtheory:-phi(n+9))::integer, [seq(seq(3*i+j,j=1..2),i=0..1000)]); # _Robert Israel_, Jan 10 2019
%t Select[Range[1, 5000], Divisible[DivisorSigma[1, #], EulerPhi[9 + #]] && ! Mod[#, 3] == 0 &] (* _David Nacin_, Mar 04 2012 *)
%o (PARI) is(n)=n%3 && sigma(n)%eulerphi(n+9)==0 \\ _Charles R Greathouse IV_, Sep 25 2012
%Y Cf. A015827.
%K nonn
%O 1,1
%A _Robert G. Wilson v_
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