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 A273881 #13 Jul 23 2025 15:40:21 %S A273881 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 A273881 26,27,28,29,30,31,40,32,41,42,44,45,46,34,47,43,48,49,50,51,52,54,55, %U A273881 56,57,58,59,60,35,61,62,64,65,66,67,68,69,70,71,72,74,53,75,76,77,78,63,36,79,80,81,82,84,85,86,87,88,89,90,91,92,94,95,96,97,98,99,100,73,101 %N A273881 Pick any pair of "3" digits in the sequence. Those two "3"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 A273881 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 A273881 Eric Angelini, <a href="/A273881/b273881.txt">Table of n, a(n) for n = 1..1011</a> %Y A273881 See A273376 for the equivalent sequence dealing with digit-"1" pairs instead of "3" %K A273881 nonn,base %O A273881 1,3 %A A273881 _Eric Angelini_ and _Jean-Marc Falcoz_ Jun 02 2016