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.

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, 330

Offset: 0

Author

Amarnath Murthy, Aug 31 2003

Keywords

• more
• nonn

Comments

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

a(38) = 336. - Max Alekseyev, Apr 29 2022

Crossrefs

Cf. A000042, A001221, A002275, A095370.

Programs

PARI

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

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

a(36) from Max Alekseyev, Apr 29 2022