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 A163170 #15 Dec 28 2024 13:31:14 %S A163170 9,15,21,27,33,45,51,63,65,85,93,99,119,129,153,165,189,195,219,231, %T A163170 255,273,297,325,341,365,381,387,403,427,455,471,495,511,513,561,585, %U A163170 633,645,693,717,765,771,819,843,891,903,951,975,1023,1025,1057,1105,1137 %N A163170 Odd composite integers that are palindromes when written in binary. %H A163170 Robert Israel, <a href="/A163170/b163170.txt">Table of n, a(n) for n = 1..10000</a> %p A163170 rev := proc (n) local nn: nn := convert(n, base, 10): add(nn[j]*10^(nops(nn)-j), j = 1 .. nops(nn)) end proc: a := proc (n) local n2: n2 := convert(n, binary): if 1 < n and `mod`(n, 2) = 1 and isprime(n) = false and rev(n2) = n2 then n else end if end proc: seq(a(n), n = 1 .. 1500); # _Emeric Deutsch_, Jul 24 2009 %t A163170 Select[Range[1,1201,2],CompositeQ[#]&&IntegerDigits[#,2]==Reverse[IntegerDigits[#,2]]&] (* _Harvey P. Dale_, Dec 28 2024 *) %Y A163170 Cf. A016041. %K A163170 base,nonn %O A163170 1,1 %A A163170 _Leroy Quet_, Jul 22 2009 %E A163170 Extended by _Emeric Deutsch_, Jul 24 2009