This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A015849 #18 Jan 10 2019 10:23:12 %S A015849 5,7,10,31,47,79,127,145,161,223,238,239,355,367,371,376,418,455,463, %T A015849 479,748,863,1039,1045,1087,1103,1118,1327,1423,1439,1567,1583,1823, %U A015849 1886,1999,2065,2108,2143,2201,2207,2239,2447,2461,2687,2767,2840,2927,2975 %N A015849 Numbers n such that phi(n + 9) | sigma(n) for n not congruent to 0 (mod 3). %C A015849 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 A015849 Robert Israel, <a href="/A015849/b015849.txt">Table of n, a(n) for n = 1..10000</a> %p A015849 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 A015849 Select[Range[1, 5000], Divisible[DivisorSigma[1, #], EulerPhi[9 + #]] && ! Mod[#, 3] == 0 &] (* _David Nacin_, Mar 04 2012 *) %o A015849 (PARI) is(n)=n%3 && sigma(n)%eulerphi(n+9)==0 \\ _Charles R Greathouse IV_, Sep 25 2012 %Y A015849 Cf. A015827. %K A015849 nonn %O A015849 1,1 %A A015849 _Robert G. Wilson v_