%I #11 Sep 08 2022 08:45:46

%S 1,1,1,2,1,2,2,4,4,2,2,4,2,4,4,8,2,8,4,4,8,4,4,8,8,4,8,8,4,8,8,12,8,6,

%T 8,24,6,8,8,8,4,16,8,8,8,8,8,16,12,16,8,12,6,16,8,16,16,8,8,16,8,16,

%U 16,36,8,16,16,12,16,16,8,32,12,12,16,16,16,16,16

%N a(n) = phi(phi(sigma(n))).

%C a(n) = A000010(A000010(A000203(n))) = A000010(A062401(n)) = A010554(A000203(n)).

%H G. C. Greubel, <a href="/A163373/b163373.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A000010(A000010(A000203(n))) = A000010(A062401(n)) = A010554(A000203(n)).

%t EulerPhi[EulerPhi[DivisorSigma[1, Range[100]]]] (* _G. C. Greubel_, Dec 20 2016 *)

%o (PARI) vector(100, n, eulerphi(eulerphi(sigma(n)))) \\ _G. C. Greubel_, Dec 20 2016

%o (Magma) [EulerPhi(EulerPhi(SumOfDivisors(n))): n in [1..80]]; // _Vincenzo Librandi_, Dec 20 2016

%Y Cf. A000010, A000203, A010554, A062401.

%K nonn

%O 1,4

%A _Jaroslav Krizek_, Jul 25 2009