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 A355504 #23 Jul 09 2022 12:14:31 %S A355504 1,0,3,2,5,4,7,6,9,8,10,20,12,22,14,24,16,26,18,28,11,21,13,23,15,25, %T A355504 17,27,19,29,30,40,32,42,34,44,36,46,38,48,31,41,33,43,35,45,37,47,39, %U A355504 49,50,60,52,62,54,64,56,66,58,68,51,61,53,63,55,65,57,67 %N A355504 Lexicographically earliest sequence of distinct nonnegative integers such that for any n >= 0, among the decimal digits of n and a(n) (counted with multiplicity) there are as many even digits as odd digits. %C A355504 Leading zeros for positive integers are ignored. %C A355504 This sequence is a self-inverse permutation of the nonnegative integers. %H A355504 Rémy Sigrist, <a href="/A355504/b355504.txt">Table of n, a(n) for n = 0..9110</a> %H A355504 Rémy Sigrist, <a href="/A355504/a355504.png">Log-log scatterplot of the sequence for n = 0..9111110</a> %H A355504 Rémy Sigrist, <a href="/A355504/a355504.gp.txt">PARI program</a> %H A355504 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A355504 a(n) = n iff n belongs to A227870. %F A355504 a(n) belongs to A352546 iff n belongs to A352547 and vice versa. %e A355504 Some terms alongside the corresponding even and odd digits are: %e A355504 n a(n) even odd %e A355504 --- ---- ----- ----- %e A355504 0 1 0 1 %e A355504 1 0 0 1 %e A355504 2 3 2 3 %e A355504 3 2 2 3 %e A355504 4 5 4 5 %e A355504 5 4 4 5 %e A355504 6 7 6 7 %e A355504 7 6 6 7 %e A355504 8 9 8 9 %e A355504 9 8 8 9 %e A355504 10 10 00 11 %e A355504 11 20 20 11 %e A355504 12 12 22 11 %e A355504 13 22 22 13 %e A355504 14 14 44 11 %e A355504 ... ... ... ... %e A355504 90 90 00 99 %e A355504 91 1000 000 911 %e A355504 92 92 22 99 %e A355504 93 1002 002 931 %e A355504 94 94 44 99 %e A355504 95 1004 004 951 %e A355504 96 96 66 99 %e A355504 97 1006 006 971 %e A355504 98 98 88 99 %e A355504 99 1008 008 991 %e A355504 100 101 000 111 %o A355504 (PARI) See Links section. %Y A355504 Cf. A227870 (fixed points), A352546, A352547, A352760. %K A355504 nonn,base %O A355504 0,3 %A A355504 _Rémy Sigrist_, Jul 05 2022