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%I #8 Nov 09 2024 21:35:55
%S 1,1,2,2,3,2,5,2,4,3,7,2,8,2,6,5,7,2,11,2,8,5,11,2,12,3,9,4,14,2,18,2,
%T 7,6,12,5,16,2,10,6,19,2,22,2,9,9,16,2,19,3,13,6,18,2,20,5,14,7,21,2,
%U 28,2,10,9,17,5,29,2,17,6,31,2,23,2,10,9,23,5,32,2,16,5,26,2,28,6,14,9
%N Number of solutions to the equation n^x==1 (mod x), 1<=x<=n.
%F Conjecture: for n>100, Sum_{k=1..n} a(k) > n^(3/2).
%o (PARI) a(n)=sum(i=1,n,if((n^i-1)%i,0,1))
%K easy,nonn
%O 1,3
%A _Benoit Cloitre_, Aug 21 2002