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

%I A104482 #29 Sep 08 2022 08:45:17
%S A104482 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,
%T A104482 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,
%U A104482 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
%N A104482 Number of distinct prime divisors of 11...119 (with n 1's).
%H A104482 Amiram Eldar, <a href="/A104482/b104482.txt">Table of n, a(n) for n = 0..204</a>
%H A104482 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/11119.htm#factor">Factorizations of 11...119</a>.
%H A104482 Markus Tervooren, <a href="http://factordb.com/index.php?query=%2810%5Ex%2B71%29%2F9">Factorizations of (1)w9</a>
%F A104482 a(n) = A001221(A165247(n+1)). - _Amiram Eldar_, Jan 24 2020
%e A104482 The number of distinct prime divisors of 19 is 1 (prime).
%e A104482 The number of distinct prime divisors of 119 is 2: 119 = 7 * 17.
%e A104482 The number of distinct prime divisors of 1119 is 2: 1119 = 3 * 373.
%p A104482 seq(nops(numtheory:-factorset((10^n + 71)/9)), n=1..70); # _Robert Israel_, Apr 19 2015
%t A104482 Table[PrimeNu[(10^n + 71)/9], {n, 50}] (* _Alonso del Arte_, Apr 18 2015 *)
%o A104482 (Magma) [(#(PrimeDivisors((10^n+71)div 9))): n in [1..60]]; // _Vincenzo Librandi_, Apr 19 2015
%Y A104482 Cf. A001221, A165247.
%K A104482 nonn,base
%O A104482 0,3
%A A104482 _Parthasarathy Nambi_, Apr 18 2005