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%I #13 Jun 06 2021 11:46:51
%S 1,1,1,3,2,2,2,4,1,2,3,2,3,3,2,4,1,3,2,1,1,2,4,2,3,4,1,4,4,4,3,2,4,3,
%T 3,4,3,5,3,7,2,1,3,4,3,6,3,6,4,2,3,3,6,5,3,3,5,3,4,3,5,4,5,4,1,8,5,5,
%U 2,6,3,3,3,3,3,3,2,4,4,4,7,5,5,6,3,2,2
%N Number of distinct prime divisors of 66...661 (with n 6s).
%C Also number of distinct prime factors of 6/9*(10^(n + 1) - 1) - 5. - _Stefan Steinerberger_, Feb 26 2006
%H Amiram Eldar, <a href="/A104890/b104890.txt">Table of n, a(n) for n = 1..199</a>
%F a(n) = A001221(A173805(n+1)). - _Amiram Eldar_, Jan 24 2020
%e Number of distinct prime divisors of 61 is 1 (prime).
%e Number of distinct prime divisors of 661 is 1 (prime).
%e Number of distinct prime divisors of 6661 is 1 (prime).
%t Table[Length[FactorInteger[6/9*(10^(n + 1) - 1) - 5]], {n, 1, 50}] (* _Stefan Steinerberger_, Feb 26 2006 *)
%t Table[PrimeNu[FromDigits[PadLeft[{1},n,6]]],{n,2,90}] (* _Harvey P. Dale_, Jun 06 2021 *)
%Y Cf. A001221, A104564, A173805.
%K nonn,base
%O 1,4
%A _Parthasarathy Nambi_, Apr 24 2005
%E More terms from _Stefan Steinerberger_, Feb 26 2006
%E Offset corrected and more terms added by _Amiram Eldar_, Jan 24 2020
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