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 A123760 #10 Mar 28 2022 07:40:21
%S A123760 9,11,13,15,18,22,26,30,36,44,52,60,72,88,104,120,144,176,208,240,288,
%T A123760 352,416,480,576,704,832,960,1152,1408,1664,1920,2304,2816,3328,3840,
%U A123760 4608,5632,6656,7680,9216,11264,13312,15360,18432,22528,26624
%N A123760 Numbers whose binary expansion is 1xy100...0 where x,y = 0 or 1.
%H A123760 Amiram Eldar, <a href="/A123760/b123760.txt">Table of n, a(n) for n = 1..10000</a>
%F A123760 a(n) = 2*a(n-4) for n > 4.
%F A123760 A093873(a(n)) = 3.
%F A123760 Sum_{n>=1} 1/a(n) = 4448/6435. - _Amiram Eldar_, Mar 28 2022
%t A123760 Union[Join @@ (Table[FromDigits[Join[#, Table[0, {n}]], 2], {n, 0, 11}] & /@ {{1, 0, 0, 1}, {1, 0, 1, 1}, {1, 1, 0, 1}, {1, 1, 1, 1}})] (* _Amiram Eldar_, Mar 28 2022 *)
%Y A123760 Cf. A029744, A070875, A070876, A093873.
%K A123760 nonn,base
%O A123760 1,1
%A A123760 _Reinhard Zumkeller_, Oct 13 2006