A163375 a(n) = sigma(tau(phi(n))).

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

Offset: 1

Author

Jaroslav Krizek, Jul 25 2009

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

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

Programs

Magma

[SumOfDivisors(NumberOfDivisors(EulerPhi(n))): n in [1..80]]; // Vincenzo Librandi, Dec 20 2016

Mathematica

DivisorSigma[1, DivisorSigma[0, EulerPhi[Range[100]]]] (* G. C. Greubel, Dec 20 2016 *)

PARI

vector(100, n, sigma(numdiv(eulerphi(n)))) \\ G. C. Greubel, Dec 20 2016

Formula

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