This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A105971 #13 Apr 05 2023 17:38:55
%S A105971 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,
%T A105971 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,
%U A105971 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
%N A105971 Number of distinct prime divisors of 66...667 (with n 6's).
%H A105971 Amiram Eldar, <a href="/A105971/b105971.txt">Table of n, a(n) for n = 0..206</a>
%F A105971 a(n) = A001221(A067275(n+2)). - _Amiram Eldar_, Jan 27 2020
%e A105971 The number of distinct prime divisors of 67 is 1 (prime).
%e A105971 The number of distinct prime divisors of 667 is 2.
%e A105971 The number of distinct prime divisors of 6667 is 2.
%t A105971 Table[PrimeNu[(6*10^(n + 1) + 3)/9], {n, 0, 30}] (* _Amiram Eldar_, Jan 27 2020 *)
%t A105971 Table[PrimeNu[FromDigits[PadLeft[{7},n,6]]],{n,100}] (* _Harvey P. Dale_, Apr 05 2023 *)
%Y A105971 Cf. A001221, A067275, A104889, A104524.
%K A105971 nonn,base
%O A105971 0,3
%A A105971 _Parthasarathy Nambi_, Apr 28 2005