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 A108686 #22 Mar 30 2024 21:19:09 %S A108686 0,10,21,30,42,51,63,70,84,92,1501,1613,1720,1834,1942,115510,611176, %T A108686 1183119 %N A108686 Increasing sequence all of whose successive digits are the digits of A108202. %C A108686 The even-indexed digits are the digits of the "natural counting digits": 1, 2, 3, ... 8, 9, 1, 0, 1, 1, 1, 2, 1, 3 ... %H A108686 Clark Kimberling, <a href="http://faculty.evansville.edu/ck6/integer/fractals.html">fractal sequences</a>. %e A108686 a(11)=1501 and not 150 because then the sequence grows quicker: 150 1161 31720 183419 421155 1061117 6118311 ... %Y A108686 Cf. A003602, A007376, A025480, A108202. %K A108686 base,nonn,more,less %O A108686 0,2 %A A108686 _Alexandre Wajnberg_, Jun 18 2005