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%I #22 May 12 2017 10:24:40
%S 0,0,0,1,0,0,0,3,0,0,0,3,0,0,3,0,1,2,0,0,3,0,3,0,0,3,0,0,0,7,0,0,5,0,
%T 3,2,0,3,0,3,0,0,0,3,0,15,4,0,3,2,0,0,3,2,3,0,0,1,0,0,15,0,3,0,0,35,0,
%U 3,0,3,0,0,3,0,0,0,15,0,0,0,3,2,0,3,0,7
%N Number of integers b with 1 < b < c such that b^(c-1) == 1 (modulo c), where c is the n-th composite number.
%C a(n) > 1 iff c is a term of A039769, i.e., iff A268310(n) > 0.
%e For n = 8: A002808(8) = 15 and b^(15-1) == 1 (modulo 15) for three values of b with 1 < b < c, namely 4, 11, 14, so a(8) = 3.
%t DeleteCases[Table[If[CompositeQ@ n, Count[Range[2, n - 1], b_ /; Mod[b^(n - 1), n] == 1], -1], {n, 117}], -1] (* _Michael De Vlieger_, May 09 2017 *)
%o (PARI) forcomposite(c=1, 200, my(i=0); for(b=2, c-1, if(Mod(b, c)^(c-1)==1, i++)); print1(i, ", "))
%Y Cf. A002808, A039769, A268310.
%K nonn
%O 1,8
%A _Felix Fröhlich_, May 09 2017
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