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%I #16 Nov 24 2024 11:28:23
%S 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 60,64,66,70,72,78,80,82,84,88,92,96,100,102,104,106,108,112,116,120,
%U 126,128,130,132,136,138,140,144,148,150,156,160,162,164,166,168,172,176
%N Values of totient function applied to squarefree numbers; or numbers of form Product (p_i-1) where p_i are distinct primes.
%H Max Alekseyev, <a href="https://oeis.org/wiki/User:Max_Alekseyev/gpscripts">PARI/GP Scripts for Miscellaneous Math Problems</a> (invphi.gp).
%F Numbers n such that n = phi(k) and |mu(k)| = 1.
%e 8,120,48 are here as totient functions of squarefree numbers 15, 143, 210. 54 and 110, 294, 342 are missing since there are no squarefree k such that phi(k) = 54, 110, etc.
%o (PARI) isok(n) = {my(v = invphi(n)); (#v) && (#select(x->issquarefree(x), v));} \\ _Michel Marcus_, Feb 25 2019
%Y Terms of A049200 after ordering and omitting multiple occurrences.
%Y Cf. A000010, A005117, A013929, A002174, A002202, A049200.
%K nonn
%O 1,2
%A _Labos Elemer_