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 A351378 #35 Feb 13 2022 14:19:50 %S A351378 1,2,3,6,4,11,5,28,7,68,8,13,9,288,10,14,12,21,15,48,16,23,17,88,18, %T A351378 30,19,488,20,34,22,32,24,45,25,26,27,66,29,268,31,44,33,84,35,286,36, %U A351378 63,37,668,38,43,39,888,40,56,41,58,42,54,46,47,49,86,50,64,51,168,52,62,53,448,55,686,57,2688,59 %N A351378 For all a(2n) the cumulative sum of the even digits used so far in the sequence [including a(2n)] is twice the cumulative sum of the odd digits used so far in the sequence [including a(2n)]. This is the lexicographically earliest sequence of distinct positive numbers with this property. %C A351378 The sequence is a permutation of the positive integers. %H A351378 Carole Dubois, <a href="/A351378/b351378.txt">Table of n, a(n) for n = 1..10000</a> %H A351378 Eric Angelini, <a href="http://cinquantesignes.blogspot.com/2022/02/une-merveille-avec-a2n.html">Une merveille avec a(2n)</a>, Feb 8, 2022, personal blog (in French). %H A351378 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %e A351378 This sequence : 1, 2, 3, 6, 4, 11, 5, 28, 7, 68, 8, 13, 9, 288, 10, 14, 12 ... %e A351378 Even dig. sums: 0, 2, 2, 8, 12, 12, 12, 22, 22, 36, 44, 44, 44, 62, 62, 66, 68 ... %e A351378 Odd dig. sums : 1, 1, 4, 4, 4, 6, 11, 11, 18, 18, 18, 22, 31, 31, 32, 33, 34 ... %e A351378 x x x x x x x x ... %e A351378 We see that 2 is twice 1, 8 is twice 4, 12 is twice 6, 22 is twice 11, 36 is twice 18, etc. %Y A351378 Cf. A036301, A351406. %K A351378 base,nonn %O A351378 1,2 %A A351378 _Eric Angelini_ and _Carole Dubois_, Feb 09 2022