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 A015856 #22 Sep 08 2022 08:44:40 %S A015856 1,2,3,4,5,7,12,13,14,20,28,29,32,36,44,45,52,53,56,60,66,77,84,86, %T A015856 104,105,108,110,123,130,144,172,221,228,238,270,287,312,342,366,380, %U A015856 385,396,441,468,558,584,585,588,644,672,750,754,760,854,864 %N A015856 Numbers k such that phi(k) | sigma(k + 10). %H A015856 G. C. Greubel, <a href="/A015856/b015856.txt">Table of n, a(n) for n = 1..1000</a> %t A015856 Select[Range[1000], Divisible[DivisorSigma[1,#+10], EulerPhi[#]] &] (* _Amiram Eldar_, Dec 13 2018 *) %o A015856 (PARI) is(n)=!(sigma(n+10)%eulerphi(n)) \\ _Charles R Greathouse IV_, Sep 25 2012 %o A015856 (Magma) [n: n in [1..900] | DivisorSigma(1,n+10) mod EulerPhi(n) eq 0]; // _G. C. Greubel_, Dec 13 2018 %Y A015856 Cf. A015834 (m=1), A015837 (m=2), A015840 (m=3), A015841 (m=4), A015843 (m=5), A015844 (m=6), A015845 (m=7), A015851 (m=8), A015853 (m=9), this sequence (m=10), A015858 (m=11), A015859 (m=12), A015860 (m=13). %K A015856 nonn %O A015856 1,2 %A A015856 _Robert G. Wilson v_ %E A015856 Missing a(1)=1 inserted by _Sean A. Irvine_, Dec 13 2018