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 A015827 #24 Jan 10 2019 10:23:04 %S A015827 3,5,7,10,15,21,24,30,31,33,42,47,57,69,78,79,93,102,114,127,129,135, %T A015827 145,161,174,177,186,210,213,216,223,231,237,238,239,249,258,264,270, %U A015827 282,297,309,318,355,367,371,376,393,399,402,417,418,435,438,455,456 %N A015827 Numbers k such that phi(k + 9) | sigma(k). %C A015827 Includes 6*A023204. Thus Dickson's conjecture implies the sequence is infinite. - _Robert Israel_, Jan 10 2019 %H A015827 Vincenzo Librandi, <a href="/A015827/b015827.txt">Table of n, a(n) for n = 1..3000</a> %p A015827 filter:= n -> (numtheory:-sigma(n)/numtheory:-phi(n+9))::integer: %p A015827 select(filter, [$1..1000]); # _Robert Israel_, Jan 10 2019 %t A015827 Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[9 + #]] &] (* _David Nacin_, Mar 01 2012 *) %o A015827 (PARI) is(n)=sigma(n)%(eulerphi(n)+9)==0 \\ _Charles R Greathouse IV_, Sep 25 2012 %Y A015827 Cf. A015849, A023204. %K A015827 nonn %O A015827 1,1 %A A015827 _Robert G. Wilson v_