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 A269169 #11 Feb 23 2016 12:08:36
%S A269169 1,2,3,4,5,6,6,7,8,9,10,11,11,11,12,13,14,15,16,17,18,19,20,21,21,21,
%T A269169 21,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,41,
%U A269169 41,41,41,41,41,42,42,43,44,45,46,47,48,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66
%N A269169 The least monotonic left inverse for A269164.
%C A269169 a(n) = number of terms of A269164 <= n.
%H A269169 Antti Karttunen, <a href="/A269169/b269169.txt">Table of n, a(n) for n = 1..8192</a>
%F A269169 Other identities. For all n >= 1:
%F A269169 a(A269164(n)) = n.
%t A269169 terms = 100; Clear[f]; f[max_] := f[max] = (s = Sort[Table[BitXor[n, BitOr[ 2 n, 4 n]], {n, 0, max}]]; Complement[Range[Last[s]], s][[1 ;; terms]]); f[terms]; f[max = 2 terms]; While[Print[max]; f[max] != f[max/2], max = 2 max]; A269164 = f[max]; a[n_] := Count[A269164, k_ /; k <= n]; Table[ a[n], {n, 1, Length[A269164]}] (* _Jean-François Alcover_, Feb 23 2016 *)
%o A269169 (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o A269169 (define A269169 (LEFTINV-LEASTMONO 1 1 A269164))
%Y A269169 Cf. A269164, A269167.
%K A269169 nonn
%O A269169 1,2
%A A269169 _Antti Karttunen_, Feb 21 2016