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 A339878 #30 Dec 23 2024 14:53:46
%S A339878 1729,3069196417,23915494401,1334063001601,6767608320001,
%T A339878 33812972024833,1584348087168001,1602991137369601,6166793784729601,
%U A339878 1531757211193440001,84388996672599528001
%N A339878 Carmichael numbers k such that phi(k) divides p*(k - 1) for some prime factor p of k - 1.
%C A339878 The first ten terms are all in A339818, none is in A339869, and all except a(2) and a(6) are in A339909.
%C A339878 Also, for all ten, a(n) == 1 (mod 64). (Cf. a similar comment in A338998).
%H A339878 Claude Goutier, <a href="http://www-labs.iro.umontreal.ca/~goutier/OEIS/A055553/">Compressed text file carm10e22.gz containing all the Carmichael numbers up to 10^22</a>.
%H A339878 Thomas Ordowski and Amiram Eldar, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2019-February/019260.html">A new look at the Lehmer's totient problem</a>, SeqFan, February 10 2019.
%t A339878 carmichaels = Cases[Import["https://oeis.org/A002997/b002997.txt", "Table"], {_, _}][[;; , 2]]; q[n_] := Module[{p = FactorInteger[n - 1][[;; , 1]], phi = EulerPhi[n]}, AnyTrue[(n - 1)*p, Divisible[#, phi] &]]; Select[carmichaels, q] (* _Amiram Eldar_, Dec 26 2020 *)
%Y A339878 Intersection of A002997 and A338998.
%Y A339878 Cf. also A339818, A339869, A339909.
%K A339878 nonn,more
%O A339878 1,1
%A A339878 _Antti Karttunen_ (after _Thomas Ordowski_'s and _Amiram Eldar_'s SeqFan-posting), Dec 26 2020
%E A339878 a(10) from _Amiram Eldar_, Dec 26 2020
%E A339878 a(11) calculated using data from _Claude Goutier_ and added by _Amiram Eldar_, Apr 21 2024