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 A104902 #21 Dec 04 2019 18:19:17
%S A104902 210,1848,2970,3720,6270,26796,38340,53940,59340,60960,70686,78210,
%T A104902 80940,88536,129540,142290,149226,155064,174174,237000,249210,300390,
%U A104902 350610,385710,429408,526110,604128,624840,664608,827310,828072,842010,848040,906528
%N A104902 Numbers n such that sigma(n) = 12*phi(n).
%C A104902 If p>2 and 2^p-1 is prime (a Mersenne prime) then 15*2^(p-2)*(2^p-1) is in the sequence. So 15*2^(A000043-2)*(2^A000043-1) is a subsequence of this sequence.
%H A104902 Amiram Eldar, <a href="/A104902/b104902.txt">Table of n, a(n) for n = 1..10000</a> (calculated using data from Jud McCranie, terms 1..1000 from Donovan Johnson)
%H A104902 Kevin A. Broughan and Daniel Delbourgo, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL16/Broughan/broughan26.html">On the Ratio of the Sum of Divisors and Euler’s Totient Function I</a>, Journal of Integer Sequences, Vol. 16 (2013), Article 13.8.8.
%H A104902 Kevin A. Broughan and Qizhi Zhou, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL17/Broughan/bro32.html">On the Ratio of the Sum of Divisors and Euler's Totient Function II</a>, Journal of Integer Sequences, Vol. 17 (2014), Article 14.9.2.
%e A104902 p>2, q=2^p-1(q is prime); m=15*2^(p-2)*q so sigma(m)=24*(2^(p-1)-1)*2^p=12*(8*2^(p-3)*(2^p-2))=12*phi(m) hence m is in the sequence.
%e A104902 sigma(237000)=748800=12*62400=12*phi(237000) so 237000 is in the sequence but 237000 is not of the form 15*2^(p-2)*(2^p-1).
%t A104902 Do[If[DivisorSigma[1, m] == 12*EulerPhi[m], Print[m]], {m, 1200000}]
%o A104902 (PARI) is(n)=sigma(n)==12*eulerphi(n) \\ _Charles R Greathouse IV_, May 09 2013
%Y A104902 Cf. A000043, A062699, A068390, A104900, A104901.
%K A104902 easy,nonn
%O A104902 1,1
%A A104902 _Farideh Firoozbakht_, Apr 01 2005