A163375 - OEIS

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

%S 1,1,3,3,4,3,7,4,7,4,7,4,12,7,7,7,6,7,12,7,12,7,7,7,12,12,12,12,12,7,

%T 15,6,12,6,15,12,13,12,15,6,15,12,15,12,15,7,7,6,15,12,12,15,12,12,15,

%U 15,13,12,7,6,28,15,13,12,18,12,15,12,12,15,15,15

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

%H G. C. Greubel, <a href="/A163375/b163375.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A000203(A000005(A000010(n))) = A000203(A062821(n)) = A062069(A000010(n)).

%t DivisorSigma[1, DivisorSigma[0, EulerPhi[Range[100]]]] (* _G. C. Greubel_, Dec 20 2016 *)

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

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

%Y Cf. A000005, A000010, A000203, A062069, A062821.

%K nonn

%O 1,3

%A _Jaroslav Krizek_, Jul 25 2009