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 A138789 #28 May 08 2025 08:55:07
%S A138789 0,2,2,2,3,2,2,3,3,2,2,4,4,2,5,4,2,3,7,4,4,3,3,2,5,3,5,2,3,6,6,3,3,5,
%T A138789 5,7,3,3,4,3,3,4,4,5,3,5,7,3,5,6,6,5,4,5,2,6,4,6,4,4,7,6,5,5,6,9,5,5,
%U A138789 7,5,5,5,5,6,6,4,4,4,5,8,7,6,4,5,4,4,9
%N A138789 a(n) = number of distinct prime divisors of A104759(n).
%H A138789 Sean A. Irvine, <a href="/A138789/b138789.txt">Table of n, a(n) for n = 1..165</a>
%F A138789 a(n) = A001221(A104759(n)). - _Michel Marcus_, Jun 30 2024
%t A138789 lst = {}; Do[lst = Join[lst, IntegerDigits[n]], {n, 1, 50}]; Table[Length[FactorInteger[FromDigits[Reverse[lst[[Range[1,n]]]]]]], {n, 1, Length[lst]}] (* _Robert Price_, Mar 24 2015 *)
%Y A138789 Cf. A001221, A104759, A000422, A116504, A007908, A116505.
%K A138789 nonn,base
%O A138789 1,2
%A A138789 _Artur Jasinski_, Mar 30 2008
%E A138789 Entire sequence corrected by _Robert Price_, Mar 24 2015
%E A138789 More terms from _Sean A. Irvine_, Jul 21 2024