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 A120241 #24 Apr 24 2024 09:17:53
%S A120241 1,2,4,3,6,8,10,5,9,12,14,16,18,20,22,7,13,17,21,24,26,28,30,32,34,36,
%T A120241 38,40,42,44,46,11,19,25,29,33,37,41,45,48,50,52,54,56,58,60,62,64,66,
%U A120241 68,70,72,74,76,78,80,82,84,86,88,90,92,94,15,27,35,43,49,53,57,61,65
%N A120241 a(n) = (n - 2^floor(log(n)/log(2)) + 1)-th integer among those positive integers not among the earlier terms of the sequence.
%C A120241 This sequence is a permutation of the positive integers. n - 2^floor(log(n)/log(2)) + 1 = A062050(n).
%H A120241 Ivan Neretin, <a href="/A120241/b120241.txt">Table of n, a(n) for n = 1..8191</a>
%e A120241 The first 6 terms of the sequence are 1,2,4,3,6,8. Now 7 - 2^floor(log(7)/log(2)) + 1 = 4. So we want the 4th term of those positive integers not occurring among the first 6 terms of the sequence (i.e., the 4th term among 5,7,9,10,11,...). So a(7) = 10.
%t A120241 Fold[Append[#1, Complement[Range[Max[#1] + #2], #1][[#2]]] &, {1},
%t A120241 Flatten@Table[Range[2^k], {k, 6}]] (* _Ivan Neretin_, Sep 24 2021 *)
%Y A120241 Cf. A120242, A062050.
%K A120241 easy,nonn
%O A120241 1,2
%A A120241 _Leroy Quet_, Jun 11 2006
%E A120241 Extended by _Ray Chandler_, Jun 19 2006