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 A269381 #7 Mar 07 2016 12:29:28
%S A269381 0,1,2,2,3,3,3,4,5,5,5,5,6,6,6,7,8,8,8,8,8,9,9,9,10,10,10,10,11,11,11,
%T A269381 12,13,13,13,13,13,13,14,14,14,14,15,15,15,15,16,16,16,17,17,17,17,18,
%U A269381 18,18,19,19,19,19,20,20,20,21,22,22,22,22,22,22,22,23,23,23,23,24,24,24,24,25,25,25,26
%N A269381 Least monotonic left inverse of A233271.
%C A269381 a(n) = number of nonzero terms of A233271 <= n.
%H A269381 Antti Karttunen, <a href="/A269381/b269381.txt">Table of n, a(n) for n = 0..8192</a>
%F A269381 Other identities. For all n >= 0:
%F A269381 a(A233271(n)) = n.
%t A269381 nn = 90; s = NestList[# + 1 + DigitCount[#, 2, 0] &, 1, nn]; Table[Count[Take[s, n + 1], k_ /; k <= n], {n, 0, nn}] (* _Michael De Vlieger_, Mar 07 2016, after _Harvey P. Dale_ at A216431 *)
%o A269381 (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o A269381 (define A269381 (LEFTINV-LEASTMONO 0 0 A233271))
%Y A269381 Cf. A233271.
%Y A269381 Cf. also A269391.
%K A269381 nonn
%O A269381 0,3
%A A269381 _Antti Karttunen_, Mar 05 2016