A163373 a(n) = phi(phi(sigma(n))).

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, 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, 16, 36, 8, 16, 16, 12, 16, 16, 8, 32, 12, 12, 16, 16, 16, 16, 16

Offset: 1

Author

Jaroslav Krizek, Jul 25 2009

Keywords

• nonn

Comments

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

Links

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

Crossrefs

Cf. A000010, A000203, A010554, A062401.

Programs

Magma

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

Mathematica

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

PARI

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

Formula

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