A104482 Number of distinct prime divisors of 11...119 (with n 1's).

1, 1, 2, 2, 1, 1, 2, 1, 3, 2, 2, 2, 4, 3, 3, 4, 1, 2, 5, 4, 3, 4, 2, 2, 4, 2, 3, 4, 2, 3, 6, 4, 4, 2, 3, 5, 3, 5, 5, 3, 3, 4, 6, 4, 4, 3, 2, 3, 2, 1, 6, 2, 7, 2, 2, 4, 4, 3, 6, 2, 3, 2, 4, 4, 5, 4, 6, 3, 5, 5, 6, 4, 6, 5, 5, 10, 4, 3, 5, 5, 3, 7, 3, 2, 9, 5, 7, 5, 8, 5, 6, 4, 5, 5, 5, 6, 5, 2, 8, 4

Offset

0,3

Links

Amiram Eldar, Table of n, a(n) for n = 0..204

Makoto Kamada, Factorizations of 11...119.

Markus Tervooren, Factorizations of (1)w9

Formula

a(n) = A001221(A165247(n+1)). - Amiram Eldar, Jan 24 2020

Example

The number of distinct prime divisors of 19 is 1 (prime).
The number of distinct prime divisors of 119 is 2: 119 = 7 * 17.
The number of distinct prime divisors of 1119 is 2: 1119 = 3 * 373.

Maple

seq(nops(numtheory:-factorset((10^n + 71)/9)), n=1..70); # Robert Israel, Apr 19 2015

Mathematica

Table[PrimeNu[(10^n + 71)/9], {n, 50}] (* Alonso del Arte, Apr 18 2015 *)

Prog

(Magma) [(#(PrimeDivisors((10^n+71)div 9))): n in [1..60]]; // Vincenzo Librandi, Apr 19 2015

Crossrefs

Cf. A001221, A165247.

Sequence in context: A270650 A088427 A255350 * A333632 A358525 A209332

Adjacent sequences: A104479 A104480 A104481 * A104483 A104484 A104485

Keyword

nonn,base

Author

Parthasarathy Nambi, Apr 18 2005

Status

approved