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 A329127 #13 Dec 10 2019 00:20:18 %S A329127 1,11,12,2,3,31,13,32,21,14,4,5,51,15,52,22,23,33,34,41,16,6,7,71,17, %T A329127 72,24,42,25,53,35,54,43,36,61,18,8,9,91,19,92,26,62,27,73,37,74,44, %U A329127 45,55,56,63,38,81,110,10,20,201,111,112,28,82,29,93,39,94 %N A329127 Lexicographically earliest sequence of distinct positive integers such that the concatenation of the odd-indexed terms equals the concatenation of the even-indexed terms. %C A329127 Leading zeros are ignored. %H A329127 Rémy Sigrist, <a href="/A329127/b329127.txt">Table of n, a(n) for n = 1..10000</a> %H A329127 Rémy Sigrist, <a href="/A329127/a329127.gp.txt">PARI program for A329127</a> %e A329127 The first terms of the odd and even bisections are: %e A329127 +------+-+---+-+---+---+-+---+---+---+---+---+-+---+---+---+---+---+---+ %e A329127 | odd |1|1 2|3|1 3|2 1|4|5 1|5 2|2 3|3 4|1 6|7|1 7|2 4|2 5|3 5|4 3|6 1| ... %e A329127 +------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ %e A329127 | even |1 1|2|3 1|3 2|1 4|5|1 5|2 2|3 3|4 1|6|7 1|7 2|4 2|5 3|5 4|3 6|1 8| ... %e A329127 +------+---+-+---+---+---+-+---+---+---+---+-+---+---+---+---+---+---+---+ %o A329127 (PARI) See Links section. %Y A329127 Cf. A197124. %K A329127 nonn,base %O A329127 1,2 %A A329127 _Rémy Sigrist_, Nov 05 2019