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 A300907 #13 Mar 19 2018 12:35:20
%S A300907 1,2,10,12,11,20,13,21,3,22,23,24,30,4,31,14,32,34,33,40,35,41,5,42,
%T A300907 15,43,25,44,45,46,50,6,51,16,52,26,53,36,54,56,55,60,57,61,7,62,17,
%U A300907 63,27,64,37,65,47,66,67,68,70,8,71,18,72,28,73,38,74,48,75,58,76,78,77,80
%N A300907 a(n) is the least positive integer not yet in the sequence in which the largest digit of a(n-2) appears among its digits; a(1)=1, a(2)=2.
%C A300907 Starting from the term a(89)=89, every term must contain a 9.
%e A300907 For n=5, a(n-2) = 10 which has largest digit 1. The positive integers containing 1 are 1, 10, 11, 12, 13, ... (A011531). Since 1 and 10 are already in the sequence, a(5) = 11. - _Michael B. Porter_, Mar 17 2018
%t A300907 FromDigits /@ Nest[Function[a, Append[a, Block[{k = 3, d}, While[Nand[FreeQ[a, #], MemberQ[#, Max@ a[[-2]]]] &@ Set[d, IntegerDigits@ k], k++]; d]]], {{1}, {2}}, 70] (* _Michael De Vlieger_, Mar 16 2018 *)
%Y A300907 Cf. A286890.
%K A300907 nonn,base
%O A300907 1,2
%A A300907 _Enrique Navarrete_, Mar 14 2018