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 A342043 #18 Feb 28 2021 09:54:10 %S A342043 1,2,11,3,4,12,13,5,6,14,15,7,8,16,17,9,18,19,21,31,32,111,33,34,35, %T A342043 36,37,38,39,41,42,112,113,43,51,52,114,115,53,54,116,55,56,57,58,59, %U A342043 61,62,117,63,64,118,65,71,72,119,73,74,121,75,76,131,77,78,79,81,82,132,133,83,84,134,135,85 %N A342043 When a digit d is even, the next digit is < d. %C A342043 The sequence is always extended with the smallest positive integer not yet present that doesn't lead to a contradiction. %C A342043 No digit 0 is present in the sequence (as 0, being even, would block it). %H A342043 Rémy Sigrist, <a href="/A342043/b342043.txt">Table of n, a(n) for n = 1..10000</a> %H A342043 Rémy Sigrist, <a href="/A342043/a342043.gp.txt">PARI program for A342043</a> %o A342043 (PARI) See Links section. %Y A342043 Cf. A342042, A342044, A342045, A342046 and A342047 (variations on the same idea). %K A342043 base,nonn %O A342043 1,2 %A A342043 _Eric Angelini_, Feb 26 2021