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 A119435 #31 Apr 20 2022 00:02:21
%S A119435 1,2,5,3,9,7,13,4,17,12,23,10,22,18,29,6,33,24,43,16,40,31,51,14,41,
%T A119435 30,53,25,49,38,61,8,65,45,83,32,76,58,95,21,74,55,94,42,87,68,107,19,
%U A119435 78,56,100,39,91,70,113,34,89,66,112,52,104,81,125,11,129,86,163,60,148
%N A119435 a(n) = (binary reversal of n)-th integer among those positive integers not occurring earlier in the sequence.
%C A119435 This sequence is a permutation of the positive integers.
%C A119435 [Proof from _N. J. A. Sloane_, Apr 20 2022: a(n) always exists, so the sequence is infinite. Every time n is a power of 2, n-reversed is 1, and a(n) is the smallest missing number. Since there are infinitely many powers of 2, every number will eventually appear.]
%H A119435 Michael De Vlieger, <a href="/A119435/b119435.txt">Table of n, a(n) for n = 1..10000</a>, first 1000 terms from Diana L. Mecum.
%H A119435 Michael De Vlieger, <a href="/A119435/a119435.txt">Extended Table of n, a(n)</a> for n = 1..2^16.
%H A119435 Michael De Vlieger, <a href="/A119435/a119435.png">Scatterplot of a(n)</a>, n = 1..2^16.
%H A119435 Michael De Vlieger, <a href="/A119435/a119435_1.png">Log-log scatterplot of a(n)</a>, n = 1..2^16.
%H A119435 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%e A119435 12 in binary is 1100; so its binary reversal is 0011, which is 3 in decimal. Those positive integers not among the first 11 terms of the sequence are 6,8,10,11,14,..., and the third of these is 10, so a(12) = 10.
%t A119435 Block[{a = {1}, nn = 69}, Do[AppendTo[a, #] &@ Complement[Range[i + 2 nn], #][[FromDigits[#, 2] &@ Reverse@ IntegerDigits[i, 2]]] &@ a, {i, 2, nn}]; a] (* _Michael De Vlieger_, Sep 03 2017 *)
%Y A119435 Cf. A030101, A119436 (inverse).
%K A119435 easy,nonn,base,look
%O A119435 1,2
%A A119435 _Leroy Quet_, May 19 2006
%E A119435 More terms from _Diana L. Mecum_, Jul 21 2008