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 A090050 #20 Oct 10 2023 05:13:15
%S A090050 2,5,10,12,19,21,25,38,42,44,50,51,52,56,71,75,76,77,83,85,89,100,101,
%T A090050 102,105,108,113,142,147,150,153,154,155,166,170,172,178,179,180,184,
%U A090050 199,201,202,203,204,205,210,211,212,217,226,227,232,240,271,279,284
%N A090050 Numbers having equal length of longest contiguous block of zeros and ones in binary expansion.
%C A090050 A087117(a(n)) = A038374(a(n)), see also A000975.
%H A090050 Reinhard Zumkeller, <a href="/A090050/b090050.txt">Table of n, a(n) for n = 1..10000</a>
%H A090050 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>
%e A090050 180 -> '10110100' with A087117(180)=2 and A038374(180)=2, therefore 180 is a term.
%t A090050 zobQ[n_]:=Module[{s=Split[IntegerDigits[n,2]]},Max[Length/@Select[ s, MemberQ[ #,0]&]] == Max[Length/@Select[s,MemberQ[#,1]&]]]; Select[ Range[ 300],zobQ] (* _Harvey P. Dale_, Aug 25 2019 *)
%t A090050 Select[Range@1000, (s=Split@IntegerDigits[#,2]; Length@s>1 && Last@Differences@(Length@# & /@ Union@s) == 0) &] (* _Hans Rudolf Widmer_, Oct 10 2023 *)
%o A090050 (Haskell)
%o A090050 a090050 n = a090050_list !! (n+1)
%o A090050 a090050_list = [x | x <- [1..], a087117 x == a038374 x]
%o A090050 -- _Reinhard Zumkeller_, May 01 2012
%Y A090050 Cf. A031443 (binary digitally balanced).
%Y A090050 Cf. A000975, A038374, A087117.
%K A090050 nonn,base
%O A090050 1,1
%A A090050 _Reinhard Zumkeller_, Nov 20 2003
%E A090050 Definition corrected, thanks to _Leroy Quet_. - Sep 17 2008