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 A015844 #19 Sep 09 2019 01:20:34 %S A015844 1,2,4,5,6,8,9,14,15,18,24,36,45,50,56,60,72,86,98,114,148,180,204, %T A015844 260,264,304,315,324,370,372,420,429,434,450,456,504,546,555,602,609, %U A015844 610,615,684,738,746,760,786,792,868,960,982,988,1122,1140,1270,1314 %N A015844 Numbers k such that phi(k) | sigma(k + 6). %H A015844 Ivan Neretin, <a href="/A015844/b015844.txt">Table of n, a(n) for n = 1..1000</a> %t A015844 Select[Range[3000], Divisible[DivisorSigma[1, 6 + #], EulerPhi[#]] &] (* _David Nacin_, Mar 03 2012 *) %o A015844 (PARI) is(n)=!(sigma(n+6)%eulerphi(n)) \\ _Charles R Greathouse IV_, Sep 25 2012 %K A015844 nonn %O A015844 1,2 %A A015844 _Robert G. Wilson v_ %E A015844 a(1) = 1 inserted by _Ivan Neretin_, Feb 05 2017