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A058060 Number of distinct prime factors of d(n), the number of divisors of n. 5
0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,12

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..5000

FORMULA

a(n) = A001221(A000005(n)).

EXAMPLE

n = 120 = 8*3*5, d(n) = 16 = 2^4, a(n)=1.

MATHEMATICA

Table[PrimeNu[DivisorSigma[0, n]], {n, 1, 100}] (* G. C. Greubel, May 05 2017 *)

PROG

(PARI) a(n)=omega(numdiv(n)) \\ Charles R Greathouse IV, May 05 2017

CROSSREFS

Cf. A001221, A000005, A058061.

Sequence in context: A174435 A294883 A088530 * A088323 A003652 A071625

Adjacent sequences:  A058057 A058058 A058059 * A058061 A058062 A058063

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 23 2000

STATUS

approved

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Last modified November 17 20:53 EST 2018. Contains 317278 sequences. (Running on oeis4.)