OFFSET
1,3
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
tau(tau(phi(7))) = tau(tau(6)) = tau(4) = 3. Thus a(7) = 3. - Derek Orr, Jul 27 2014
MATHEMATICA
DivisorSigma[0, DivisorSigma[0, EulerPhi[Range[90]]]] (* Harvey P. Dale, Mar 25 2016 *)
PROG
(Magma) [NumberOfDivisors(NumberOfDivisors(EulerPhi(n))): n in [1..100]]; // Vincenzo Librandi, Jul 27 2014
(PARI) a(n)=sigma(sigma(eulerphi(n), 0), 0); \\ Derek Orr, Jul 27 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Jul 25 2009
EXTENSIONS
More terms from Vincenzo Librandi, Jul 27 2014
STATUS
approved