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%I #8 Dec 21 2016 02:43:13
%S 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,2,1,1,1,1,
%T 1,2,1,1,1,2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,2,1,1,1,2,1,2,1,1,
%U 1,2,1,2,1,1,1,1,1,2,1,2,2,1,1,2,1,1,1,2,1,2,1,1,1,1,1,2
%N a(n) = phi(phi(tau(n))).
%H G. C. Greubel, <a href="/A163379/b163379.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = A000010(A000010(A000005(n))) = A000010(A163109(n)) = A010554(A000005(n)).
%t EulerPhi[EulerPhi[DivisorSigma[0, Range[100]]]] (* _G. C. Greubel_, Dec 20 2016 *)
%o (PARI) vector(100, n, eulerphi(eulerphi(numdiv(n)))) \\ _G. C. Greubel_, Dec 20 2016
%Y Cf. A000005, A000010, A010554, A163109.
%K nonn
%O 1,16
%A _Jaroslav Krizek_, Jul 25 2009
%E More terms added by _G. C. Greubel_, Dec 20 2016