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 A137673 #9 Jul 27 2023 09:44:38
%S A137673 1,3,4,6,7,9,12,14,15,20,22,28,30,32,34,41,45,47,48,50,51,54,59,62,63,
%T A137673 67,69,71,74,76,83,87,93,94,95,99,100,107,110,113,114,116,119,128,133,
%U A137673 135,140,142,143,150,153,155,156,161,163,166,167,170,183,186,188,191
%N A137673 Smallest m such that A137671(m) = n.
%H A137673 Reinhard Zumkeller, <a href="/A137673/b137673.txt">Table of n, a(n) for n = 1..2000</a>
%F A137673 A137671(a(n)) = n and A137671(m) < n for m < a(n).
%F A137673 A137674(n) = a(A137671(A137674(n)-1)) + 1.
%t A137673 b[1] = 1; b[n_] := b[n] = Count[Array[s, n - 1], s[n - 1]]; s[n_] := s[n] = DigitCount[b[n], 2, 1]; seq[len_, nmax_] := Module[{t = Table[0, {len}], c = 0, n = 1, i}, While[c < len && n < nmax, i = b[n]; If[t[[i]] == 0, c++; t[[i]] = n]; n++]; t]; seq[100, 1000] (* _Amiram Eldar_, Jul 27 2023 *)
%Y A137673 Cf. A137671, A137674.
%K A137673 nonn,base
%O A137673 1,2
%A A137673 _Reinhard Zumkeller_, Feb 05 2008