A163379 a(n) = phi(phi(tau(n))).

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, 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, 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

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, A010554, A163109.

Programs

Mathematica

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

PARI

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

Formula

a(n) = A000010(A000010(A000005(n))) = A000010(A163109(n)) = A010554(A000005(n)).

Extensions

More terms added by G. C. Greubel, Dec 20 2016