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 A173023 #13 Oct 15 2024 15:42:39
%S A173023 1,2,3,3,4,5,5,6,7,8,9,9,9,9,10,11,12,13,14,14,15,16,16,17,17,17,17,
%T A173023 17,18,19,20,21,22,23,24,24,25,26,26,27,28,29,30,30,30,30,31,32,32,32,
%U A173023 32,32,32,32,32,32,33,34,35,35,36,37,38,39,40,41,42,42,43,44,44,45,46,47
%N A173023 Number of numbers <= n whose binary representation contains no isolated digits "11".
%H A173023 Reinhard Zumkeller, <a href="/A173023/b173023.txt">Table of n, a(n) for n = 0..10000</a>
%F A173023 a(A173025(n+1)) = a(A173025(n)) + 1.
%F A173023 A173021(n) <= A173022(n) <= a(n).
%e A173023 a(20) = #{0,1,2,4,5,7,8,9,10,14,15,16,17,18,20} = #{0,1,10,100,101,111,1000,1001,1010,1110,1111,10000,10001,10010,10100} = 15.
%t A173023 Accumulate[Table[If[Count[Split[IntegerDigits[n,2]],{1,1}]>0,0,1],{n,0,80}]] (* _Harvey P. Dale_, Feb 12 2017 *)
%Y A173023 Cf. A007088, A173021, A173022, A173025.
%K A173023 base,nonn
%O A173023 0,2
%A A173023 _Reinhard Zumkeller_, Feb 07 2010