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 A043719 #10 Jun 18 2021 23:03:56 %S A043719 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,17,34,51,68,85,102,119,136,153, %T A043719 170,187,204,221,238,255,257,258,259,260,261,262,263,264,265,266,267, %U A043719 268,269,270,271,273,288,289,291,292,293,294,295 %N A043719 Numbers whose base-16 representation has an odd number of runs. %o A043719 (Python) %o A043719 from itertools import groupby %o A043719 def ok(n): return len(list(g for k, g in groupby(hex(n)[2:])))%2 == 1 %o A043719 print(list(filter(ok, range(1, 296)))) # _Michael S. Branicky_, Jun 18 2021 %K A043719 nonn,base %O A043719 1,2 %A A043719 _Clark Kimberling_