A163378 a(n) = sigma(phi(tau(n))).

1, 1, 1, 3, 1, 3, 1, 3, 3, 3, 1, 3, 1, 3, 3, 7, 1, 3, 1, 3, 3, 3, 1, 7, 3, 3, 3, 3, 1, 7, 1, 3, 3, 3, 3, 12, 1, 3, 3, 7, 1, 7, 1, 3, 3, 3, 1, 7, 3, 3, 3, 3, 1, 7, 3, 7, 3, 3, 1, 7, 1, 3, 3, 12, 3, 7, 1, 3, 3, 7, 1, 7, 1, 3, 3, 3, 3, 7, 1, 7, 7, 3, 1, 7, 3, 3

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, A062402, A163109.

Programs

Mathematica

Table[DivisorSigma[1,EulerPhi[DivisorSigma[0,n]]],{n,100}] (* Harvey P. Dale, Jun 21 2016 *)

PARI

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

Formula

a(n) = A000203(A000010(A000005(n))) = A000203(A163109(n)) = A062402(A000005(n)).

Extensions

More terms from Harvey P. Dale, Jun 21 2016