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%I #9 Jan 03 2017 02:31:06
%S 0,0,1,2,1,1,2,3,3,2,3,6,5,3,11,6,10,6,3,9,11,9,14,6,10,14,9,6,11,14,
%T 13,9,28,11,20,14,10,27,14,24,18,9,19,24,20,32,11,20,29,14,14,24,27,
%U 24,42,14,20,37,27,14,45,28,39,27,14,51,29,42,31,51,20,28,42,27,20,32,32
%N a(n)-th composite number = phi(n-th composite number); a(1)=a(2)=0.
%F See program.
%e Phi of 25th composite number = 10th composite number: n=25: A002808(25)=38, phi(38) = 18 = A002808(10) so a(25)=10.
%t c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x]; G[x_] := x-PrimePi[x]-1; a(n)=G[EulerPhi[c[n]]]
%Y Cf. A000010, A002808, A062298.
%K nonn
%O 1,4
%A _Labos Elemer_, Aug 05 2002
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