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A086565 Smallest k such that (10^k - 1)/9 has n distinct prime divisors. Or a(n)= smallest value of k such that A000042(k) has exactly n distinct prime divisors. 0
1, 2, 3, 9, 8, 6, 15, 12, 18, 45, 24, 32, 54, 30, 42, 64, 102, 72, 108, 154, 60, 84, 96, 140, 126, 200, 120, 204, 308, 168, 192, 280, 180, 210, 240, 252 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

a(40) = 300; all other subsequent terms are > 322. - Ray Chandler, Apr 23 2017

LINKS

Table of n, a(n) for n=0..35.

PROG

(PARI) a(n) = my(k=1); while(omega((10^k - 1)/9) !=n, k++); k; \\ Michel Marcus, Apr 23 2017

CROSSREFS

Cf. A000042, A001221, A002275, A095370.

Sequence in context: A021421 A152812 A246825 * A008291 A261525 A122665

Adjacent sequences:  A086562 A086563 A086564 * A086566 A086567 A086568

KEYWORD

more,nonn

AUTHOR

Amarnath Murthy, Aug 31 2003

EXTENSIONS

Corrected and extended by Sascha Kurz, Sep 22 2003

a(12)-a(15) from David Wasserman, Mar 28 2005

a(16)-a(27) from Donovan Johnson, Nov 17 2008

a(28)-a(35) from Ray Chandler, Apr 23 2017

STATUS

approved

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Last modified December 4 19:40 EST 2021. Contains 349526 sequences. (Running on oeis4.)