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 A273884 #10 Jun 09 2016 08:38:30 %S A273884 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25, %T A273884 26,27,28,29,30,31,32,33,34,35,37,36,38,39,40,41,42,43,44,45,46,47,48, %U A273884 49,50,51,52,53,54,55,57,58,59,56,60,61,70,62,71,72,73,74,75,77,78,79 %N A273884 Pick any pair of "6" digits in the sequence. Those two "6"s are separated by k digits. This is the lexicographically earliest sequence of distinct terms in which all the resulting values of k are distinct. %C A273884 The sequence starts with a(1)=0. It is then always extended with the smallest integer not yet present and not leading to a contradiction (which would mean producing a value of k already seen). %H A273884 Eric Angelini, <a href="/A273884/b273884.txt">Table of n, a(n) for n = 1..1011</a> %Y A273884 See A273376 for the equivalent sequence dealing with digit-"1" pairs instead of "6" %K A273884 nonn,base %O A273884 1,3 %A A273884 _Eric Angelini_ and _Jean-Marc Falcoz_, Jun 02 2016