0,3

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

Makoto Kamada, Factorizations of 11...119.

Markus Tervooren, Factorizations of (1)w9

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

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.

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

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

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

Cf. A001221, A165247.

Sequence in context: A270650 A088427 A255350 * A333632 A209332 A020945

Adjacent sequences: A104479 A104480 A104481 * A104483 A104484 A104485

nonn,base

Parthasarathy Nambi, Apr 18 2005

approved