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 A015853 #21 Sep 08 2022 08:44:40 %S A015853 1,2,3,4,5,6,10,12,13,14,21,24,26,30,31,37,42,45,48,50,57,60,68,76,78, %T A015853 96,105,111,133,156,168,175,181,196,200,215,273,286,288,290,310,320, %U A015853 336,350,361,369,381,399,406,420,450,465,543,585,600,612,656,740 %N A015853 Numbers k such that phi(k) | sigma(k + 9). %H A015853 G. C. Greubel, <a href="/A015853/b015853.txt">Table of n, a(n) for n = 1..1000</a> %t A015853 Select[Range[1000], Divisible[DivisorSigma[1,#+9], EulerPhi[#]] &] (* _Amiram Eldar_, Dec 13 2018 *) %o A015853 (PARI) is(n)=!(sigma(n+9)%eulerphi(n)) \\ _Charles R Greathouse IV_, Sep 25 2012 %o A015853 (Magma) [n: n in [1..900] | DivisorSigma(1,n+9) mod EulerPhi(n) eq 0]; // _G. C. Greubel_, Dec 13 2018 %Y A015853 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), this sequence (m=9), A015856 (m=10), A015858 (m=11), A015859 (m=12), A015860 (m=13). %K A015853 nonn %O A015853 1,2 %A A015853 _Robert G. Wilson v_ %E A015853 Missing a(1)=1 inserted by _Sean A. Irvine_, Dec 13 2018