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 A105972 #22 Apr 11 2020 22:01:26
%S A105972 0,1,1,2,4,3,2,2,2,2,3,3,3,3,2,2,3,8,1,3,2,2,5,2,4,6,2,2,5,3,4,4,4,2,
%T A105972 5,5,5,4,6,3,5,3,2,5,4,4,7,4,4,6,3,5,5,3,5,6,5,5,5,4,3,5,4,2,7,3,3,8,
%U A105972 3,5,6,7,3,6,3,3,7,3,1,5,5,4,8,4,3,4,4
%N A105972 Number of distinct prime divisors of 88...881 (with n 8's).
%H A105972 Amiram Eldar, <a href="/A105972/b105972.txt">Table of n, a(n) for n = 0..203</a>
%F A105972 a(n) = A001221(A173810(n+1)). - _Michel Marcus_, Jan 27 2014
%e A105972 The number of distinct prime divisors of 81 is 1.
%e A105972 The number of distinct prime divisors of 881 is 1 (prime).
%e A105972 The number of distinct prime divisors of 8881 is 2.
%t A105972 Table[PrimeNu[(8*10^(n+1) - 71)/9], {n,0,50}] (* _G. C. Greubel_, May 16 2017 *)
%t A105972 PrimeNu/@Table[10 FromDigits[PadRight[{},n,8]]+1,{n,0,90}] (* _Harvey P. Dale_, Apr 25 2019 *)
%o A105972 (PARI) a(n) = omega((8*10^(n+1)-71)/9); \\ _Michel Marcus_, Jan 27 2014
%Y A105972 Cf. A001221, A104564, A104517, A104659, A173810.
%K A105972 nonn,base
%O A105972 0,4
%A A105972 _Parthasarathy Nambi_, Apr 28 2005
%E A105972 More terms from _Michel Marcus_, Jan 27 2014