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 A174208 #15 Feb 22 2020 20:57:36 %S A174208 1,0,1,1,0,1,1,0,1,1,0,0,1,0,1,0,1,1,0,1,1,1,0,1,1,1,0,0,0,1,0,1,0,0, %T A174208 1,1,0,1,0,1,0,1,1,0,1,1,0,1,0,1,1,0,1,0,1,1,1,0,1,1,1,1,0,1,1 %N A174208 Write natural numbers in base 2 as a stream of digits. Moving left to right, delete odd occurrences of digit 0 and even occurrences of digit 1. %e A174208 Numbers in base 2: 0, 1, 10, 11, 100, 101, 110, 111, 1000..... %e A174208 Stream of digits: 0110111001011101111000... %e A174208 Delete odd occurrences of 0 (replace by ~): ~110111~01~11101111~0~... %e A174208 Delete even occurrences of 1 (replace by ~): ~1~01~1~0~~1~10~1~1~0~... %e A174208 This leaves the digits: 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,.... %Y A174208 Cf. A030190, A174203-A174207, A174209, A174210. %K A174208 easy,nonn,base %O A174208 0,1 %A A174208 _Paolo P. Lava_ and _Giorgio Balzarotti_, Mar 15 2010 %E A174208 Edited by _N. J. A. Sloane_, Aug 21 2012