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A141242 a(n) is the number of divisors of the n-th positive integer with a prime number of divisors. In other words a(n) is the number of divisors of A009087(n). 7
2, 2, 3, 2, 2, 3, 2, 2, 5, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 7, 2, 2, 2, 2, 5, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A009087(n) is of the form, p^(a(n)-1), where p is some prime and a(n) is the n-th term (which is prime, of course) of this sequence.

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000005(A009087(n)).

MATHEMATICA

DivisorSigma[0, #] &@ Select[Range@ 500, PrimeQ@ DivisorSigma[0, #] &] (* Michael De Vlieger, Aug 19 2017 *)

CROSSREFS

Cf. A000005, A009087, A141241.

Sequence in context: A087159 A218800 A062502 * A130451 A130285 A046027

Adjacent sequences:  A141239 A141240 A141241 * A141243 A141244 A141245

KEYWORD

nonn

AUTHOR

Leroy Quet, Jun 16 2008

EXTENSIONS

Extended by Ray Chandler, Jun 25 2009

STATUS

approved

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Last modified October 22 21:00 EDT 2021. Contains 348180 sequences. (Running on oeis4.)