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 A043540 #12 Apr 24 2021 21:30:39
%S A043540 1,1,1,1,1,1,1,1,1,1,1,1,2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,1,2,2,2,2,2,2,
%T A043540 2,2,2,2,2,2,2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,1,2,2,2,2,2,2,2,2,2,2,2,2,
%U A043540 2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,1,2,2,2,2,2,2
%N A043540 Number of distinct base-13 digits of n.
%t A043540 Table[Length[Union[IntegerDigits[n,13]]],{n,120}] (* _Harvey P. Dale_, May 12 2019 *)
%o A043540 (PARI) vector(90, n, #vecsort(digits(n,13),,8)) \\ _Michel Marcus_, Aug 19 2015
%K A043540 nonn,base
%O A043540 1,13
%A A043540 _Clark Kimberling_