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 A073858 #14 Dec 27 2024 10:47:46 %S A073858 1,2,4,9,16,18,64,100,225,242,450,516,729,1458,3872,4096,4624,13932, %T A073858 14406,17672,18225,20124,21780,28900,29262,29616,36450,45996,62500, %U A073858 65025,65536,76832,92778,95916,106092,106308,114630,114930 %N A073858 Numbers k such that sigma(phi(k)) divides phi(sigma(k)). %H A073858 Donovan Johnson, <a href="/A073858/b073858.txt">Table of n, a(n) for n = 1..1000</a> %t A073858 Select[Range[115000],Divisible[EulerPhi[DivisorSigma[1,#]],DivisorSigma[ 1,EulerPhi[ #]]]&] (* _Harvey P. Dale_, Jan 31 2021 *) %o A073858 (PARI) isok(k) = eulerphi(sigma(k)) % sigma(eulerphi(k))==0 \\ _Donovan Johnson_, Jul 05 2012 %Y A073858 Cf. A033632, A066930. %K A073858 easy,nonn %O A073858 1,2 %A A073858 _Benoit Cloitre_, Sep 02 2002