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 A105255 #18 Apr 11 2020 22:03:08
%S A105255 1,1,2,2,2,2,2,2,5,3,2,5,3,1,6,4,1,4,4,3,4,4,2,3,3,3,4,4,2,6,5,4,6,3,
%T A105255 1,5,6,2,6,4,3,7,5,2,8,7,4,7,5,4,7,3,7,5,3,3,9,6,5,3,3,3,7,3,4,6,4,2,
%U A105255 6,7,5,7,7,4,7,6,4,5,3,4,6,2,2,7,5,3,9,6,4,8,6,7,5,2,5,6,5,5,7,7
%N A105255 Number of distinct prime divisors of 88...889 (with n 8's).
%H A105255 Amiram Eldar, <a href="/A105255/b105255.txt">Table of n, a(n) for n = 0..225</a>
%F A105255 a(n) = A001221(A059482(n+1)). - _Michel Marcus_, Jan 27 2014
%e A105255 The number of distinct prime divisors of 89 is 1 (prime).
%e A105255 The number of distinct prime divisors of 889 is 2.
%e A105255 The number of distinct prime divisors of 8889 is 2.
%t A105255 Table[PrimeNu[(8*10^(n + 1) + 1)/9], {n, 0,50}] (* _G. C. Greubel_, May 16 2017 *)
%o A105255 (PARI) a(n) = omega((8*10^(n+1)+1)/9); \\ _Michel Marcus_, Jan 27 2014
%Y A105255 Cf. A104543.
%K A105255 nonn,base
%O A105255 0,3
%A A105255 _Parthasarathy Nambi_, Apr 29 2005