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A062821 Number of divisors of totient of n. 18
1, 1, 2, 2, 3, 2, 4, 3, 4, 3, 4, 3, 6, 4, 4, 4, 5, 4, 6, 4, 6, 4, 4, 4, 6, 6, 6, 6, 6, 4, 8, 5, 6, 5, 8, 6, 9, 6, 8, 5, 8, 6, 8, 6, 8, 4, 4, 5, 8, 6, 6, 8, 6, 6, 8, 8, 9, 6, 4, 5, 12, 8, 9, 6, 10, 6, 8, 6, 6, 8, 8, 8, 12, 9, 8, 9, 12, 8, 8, 6, 8, 8, 4, 8, 7, 8, 8, 8, 8, 8, 12, 6, 12, 4, 12, 6, 12, 8, 12, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..2000

FORMULA

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

EXAMPLE

The number of divisors of phi(n) can be greater than, less than, or equal to the number of divisors of n:

.

  n   phi(n)  d(phi(n))   d(n)

  ==  ======  =========   ====

  10     4        3     <   4

  11    10        4     >   2

  28    12        6     =   6

MATHEMATICA

Array[DivisorSigma[0, EulerPhi[#]]&, 110] (* Harvey P. Dale, Jul 13 2012 *)

PROG

(PARI) { for (n=1, 2000, write("b062821.txt", n, " ", numdiv(eulerphi(n))) ) } \\ Harry J. Smith, Aug 11 2009

CROSSREFS

Cf. A000005, A000010, A276044.

Sequence in context: A323164 A318881 A280338 * A296080 A180633 A286610

Adjacent sequences:  A062818 A062819 A062820 * A062822 A062823 A062824

KEYWORD

nonn

AUTHOR

Labos Elemer, Jul 20 2001

EXTENSIONS

Offset corrected by Jaroslav Krizek, Jul 24 2009

Edited by Jon E. Schoenfield, Nov 13 2016

STATUS

approved

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Last modified July 22 14:38 EDT 2019. Contains 325222 sequences. (Running on oeis4.)