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 A297781 #4 Feb 04 2018 12:42:36
%S A297781 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 A297781 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 A297781 2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,1,2,2
%N A297781 Number of distinct runs in base-13 digits of n.
%C A297781 Every positive integers occurs infinitely many times. See A297770 for a guide to related sequences.
%H A297781 Clark Kimberling, <a href="/A297781/b297781.txt">Table of n, a(n) for n = 1..10000</a>
%e A297781 5200468 in base-13: 1,1,0,1,1,0,0; four runs, of which 3 are distinct, so that a(5200468) = 3.
%t A297781 b = 13; s[n_] := Length[Union[Split[IntegerDigits[n, b]]]]
%t A297781 Table[s[n], {n, 1, 200}]
%Y A297781 Cf. A043565 (number of runs, not necessarily distinct), A297770.
%K A297781 nonn,base,easy
%O A297781 1,13
%A A297781 _Clark Kimberling_, Feb 03 2018