A104524 -id:A104524 - cp's OEIS frontend

A105248 Number of distinct prime divisors of 88...887 (with n 8's).

1, 2, 1, 1, 2, 1, 3, 3, 1, 2, 3, 1, 3, 4, 4, 4, 4, 2, 3, 3, 4, 3, 2, 3, 2, 2, 3, 5, 5, 4, 3, 4, 2, 5, 6, 2, 5, 3, 2, 3, 3, 3, 3, 3, 4, 2, 4, 2, 5, 2, 3, 5, 3, 6, 4, 5, 2, 5, 4, 3, 3, 3, 4, 2, 5, 4, 4, 5, 5, 4, 5, 1, 3, 6, 4, 2, 2, 4, 3, 4, 5, 7, 6, 5, 4, 8, 4

Offset: 0

Parthasarathy Nambi, Apr 29 2005

			The number of distinct prime divisors of 87 is 2.
The number of distinct prime divisors of 887 is 1 (prime).
The number of distinct prime divisors of 8887 is 1 (prime).

Amiram Eldar, Table of n, a(n) for n = 0..199

Cf. A104524, A104889.

Table[PrimeNu[(8*10^(n + 1) - 17)/9], {n, 1, 50}] (* G. C. Greubel, May 21 2017 *)

a(n) = omega((8*10^(n+1)-17)/9); \\ Michel Marcus, Jan 27 2014

a(n) = A001221(A173812(n+1)). - Michel Marcus, Jan 27 2014

More terms from Brian Lauer (bel136(AT)psu.edu), Feb 23 2006
Corrected and extended by Michel Marcus, Jan 27 2014
More terms from Amiram Eldar, Jan 27 2020

A105971 Number of distinct prime divisors of 66...667 (with n 6's).

Original entry on oeis.org

1, 1, 2, 2, 2, 1, 2, 1, 1, 3, 1, 3, 3, 4, 3, 3, 3, 2, 4, 1, 2, 2, 1, 2, 5, 2, 4, 4, 3, 4, 3, 3, 3, 3, 4, 3, 4, 3, 4, 2, 1, 3, 5, 4, 4, 6, 6, 5, 4, 2, 4, 4, 4, 6, 5, 4, 4, 3, 3, 5, 5, 3, 1, 4, 5, 1, 5, 5, 5, 4, 3, 2, 4, 4, 4, 4, 5, 4, 5, 6, 2, 7, 6, 4, 7, 5, 5, 4, 5, 2, 5, 4, 3, 6, 4, 6, 6, 4, 3, 5

Offset: 0

Parthasarathy Nambi, Apr 28 2005

			The number of distinct prime divisors of 67 is 1 (prime).
The number of distinct prime divisors of 667 is 2.
The number of distinct prime divisors of 6667 is 2.

Amiram Eldar, Table of n, a(n) for n = 0..206

Cf. A001221, A067275, A104889, A104524.

Table[PrimeNu[(6*10^(n + 1) + 3)/9], {n, 0, 30}] (* Amiram Eldar, Jan 27 2020 *)
Table[PrimeNu[FromDigits[PadLeft[{7},n,6]]],{n,100}] (* Harvey P. Dale, Apr 05 2023 *)

a(n) = A001221(A067275(n+2)). - Amiram Eldar, Jan 27 2020

cp's OEIS Frontend

A105248 Number of distinct prime divisors of 88...887 (with n 8's).

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