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 A049225 #27 Mar 18 2025 07:32:30
%S A049225 1,2,4,6,8,10,12,16,18,20,22,24,28,30,32,36,40,42,44,46,48,52,56,58,
%T A049225 60,64,66,70,72,78,80,82,84,88,92,96,100,102,104,106,108,112,116,120,
%U A049225 126,128,130,132,136,138,140,144,148,150,156,160,162,164,166,168,172,176
%N A049225 Values of totient function applied to squarefree numbers; or numbers of form Product (p_i-1) where p_i are distinct primes.
%C A049225 Numbers m such that m = phi(k) and |mu(k)| = 1.
%H A049225 Amiram Eldar, <a href="/A049225/b049225.txt">Table of n, a(n) for n = 1..10000</a>
%H A049225 Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%e A049225 8, 120, 48 are terms as totients of the squarefree numbers 15, 143, 210.
%e A049225 54, 110 are not terms since there are no squarefree numbers k such that phi(k) = 54, 110.
%o A049225 (PARI) isok(n) = {my(v = invphi(n)); (#v) && (#select(x->issquarefree(x), v));} \\ _Michel Marcus_, Feb 25 2019
%Y A049225 Terms of A049200 after ordering and omitting multiple occurrences.
%Y A049225 Cf. A000010, A005117, A008683, A013929, A002174, A002202, A049200.
%K A049225 nonn
%O A049225 1,2
%A A049225 _Labos Elemer_