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 A239139 #14 Jun 09 2016 10:40:43 %S A239139 1,2,3,4,5,6,7,8,9,10,12,11,20,13,14,15,16,17,18,19,21,23,22,30,24,25, %T A239139 26,27,28,29,31,32,34,33,40,35,36,37,38,39,41,42,43,45,44,50,46,47,48, %U A239139 49,51,52,53,54,56,55,60,57,58,59,61,62,63,64,65,67,66 %N A239139 The sequence S = a(1), a(2), ... is defined by a(1)=1, if d,e,f are consecutive decimal digits then we do not have d <= e = f, and S is always extended with the smallest integer not yet present in S. %C A239139 Computed by Lars Blomberg. %D A239139 Eric Angelini, Posting to Sequence Fans Mailing List, Sep 28 2013 %H A239139 Eric Angelini, <a href="http://www.cetteadressecomportecinquantesignes.com/LittleEqualGreat.htm">Less than <, Equal to =, Greater than ></a> (see sequence Sj) %H A239139 Eric Angelini, <a href="/A239083/a239083.pdf">Less than <, Equal to =, Greater than ></a> [Cached copy, with permission of the author] %Y A239139 The sequences in this family are given in A239083-A239086, A239136-A239139, A239087-A239090, A239215-A239218, A239235. %K A239139 nonn,base %O A239139 1,2 %A A239139 _Michel Marcus_, Mar 11 2014