A086565 - OEIS

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

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OFFSET

0,2

COMMENTS

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

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

LINKS

Table of n, a(n) for n=0..36.

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.