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%I #13 Mar 27 2021 07:59:55
%S 1,2,4,2,3,4,4,4,9,2,4,4,9,4,4,5,4,3,8,8,2,9,4,9,4,4,9,4,8,4,15,4,4,7,
%T 4,9,8,4,9,4,9,4,8,4,9,2,25,24,4,9,16,4,4,9,8,9,8,4,3,4,8,25,4,9,4,8,
%U 49,4,9,4,9,4,4,9,4,8,4,45,4,4,8,9,8,8,9,4,15,4,9,8,11,4,9,8,5,8,2,9,16,8,49,4,9,4,8,8,9,4,9,4,25,4,9,8,8,4,27,16,9,8,4,9,4,9,4
%N Number of elements k in Z/mZ such that k^m=k, for nonprime m = A018252(n).
%C This is a reduced version of A182816, without the "trivial" terms a(n)=n for prime indices n.
%H Amiram Eldar, <a href="/A182817/b182817.txt">Table of n, a(n) for n = 1..10000</a>
%H "Lunkwill", <a href="http://credentiality2.blogspot.com/2010/12/guess-mystery-plot.html">Carmichael numbers and Fermat primality</a>, Dec 02 2010.
%F a(n) = A182816(A018252(n)).
%t f[n_] := Times @@ ((1 + GCD[n-1, #-1]) & /@ FactorInteger[n][[;;,1]]); f /@ Select[Range[165], !PrimeQ[#] &] (* _Amiram Eldar_, Mar 27 2021 *)
%Y Cf. A018252, A182816, A002997.
%K nonn
%O 1,2
%A _M. F. Hasler_, Dec 05 2010
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