A163367 a(n) = phi(tau(sigma(n))).

1, 1, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 4, 4, 1, 2, 2, 2, 4, 2, 6, 4, 4, 1, 4, 4, 4, 4, 4, 2, 2, 4, 4, 4, 2, 2, 4, 4, 4, 4, 4, 2, 4, 4, 4, 4, 2, 2, 2, 4, 2, 4, 8, 4, 8, 4, 4, 4, 8, 2, 4, 4, 1, 4, 8, 2, 4, 4, 8, 4, 4, 2, 4, 2, 4, 4, 8, 4, 4, 2, 4, 4, 4, 4, 4

Offset: 1

Author

Jaroslav Krizek, Jul 25 2009

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A000005, A000010, A000203, A062068, A163109.

Programs

Maple

with(numtheory): A163367:=n->phi(tau(sigma(n))): seq(A163367(n), n=1..150); # Wesley Ivan Hurt, Dec 19 2016

Mathematica

Table[EulerPhi[DivisorSigma[0, DivisorSigma[1, n]]], {n, 100}] (* G. C. Greubel, Dec 19 2016 *)

PARI

vector(50, n, eulerphi(numdiv(sigma(n)))) \\ G. C. Greubel, Dec 19 2016

Formula

a(n) = A000010(A000005(A000203(n))) = A000010(A062068(n)) = A163109(A000203(n)).