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 A168354 #13 Nov 24 2020 10:25:46
%S A168354 15,21,33,51,65,85,93,119,129,219,341,365,381,403,427,471,511,633,717,
%T A168354 771,843,951,1057,1137,1241,1273,1285,1317,1397,1501,1651,1707,1799,
%U A168354 1967,2047,2049,2661,2973,3579,3687,3831,4097,4321,4369,4529,4593,4681
%N A168354 Squarefree semiprimes whose binary expansion is palindromic.
%H A168354 Amiram Eldar, <a href="/A168354/b168354.txt">Table of n, a(n) for n = 1..10000</a>
%e A168354 15 = 3*5 = {1,1,1,1}.
%e A168354 21 = 3*7 = {1,0,1,0,1}.
%e A168354 33 = 3*11 = {1,0,0,0,0,1}.
%t A168354 f1[n_]:=Reverse[IntegerDigits[n,2]]==IntegerDigits[n,2]; f2[n_]:=Last/@FactorInteger[n]=={1,1}; lst={};Do[If[f1[n]&&f2[n],AppendTo[lst,n]],{n,8!}];lst
%Y A168354 Cf. A016041.
%Y A168354 Intersection of A006995 and A006881. - _Michel Marcus_, Nov 24 2020
%K A168354 nonn,base
%O A168354 1,1
%A A168354 _Vladimir Joseph Stephan Orlovsky_, Nov 23 2009