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 A331894 #11 Jan 31 2020 04:16:18
%S A331894 0,1,3,5,7,17,21,31,51,65,85,127,195,257,273,325,341,455,511,771,819,
%T A331894 1025,1105,1285,1365,1799,2047,3075,4097,4161,4369,4433,5125,5189,
%U A331894 5397,5461,7175,7967,8191,12291,12483,13107,16385,16705,17425,17745,20485,20805
%N A331894 Positive numbers such that both their binary and negabinary representations are palindromic.
%C A331894 Numbers of the form 2^(2*m-1) - 1 (A083420) and 2^(2*m) + 1 (A052539) are terms.
%H A331894 Amiram Eldar, <a href="/A331894/b331894.txt">Table of n, a(n) for n = 1..1000</a>
%e A331894 7 is a term since the binary representation of 7, 111, and the negabinary representation of 7, 11011, are both palindromic.
%t A331894 negabin[n_] := negabin[n] = If[n==0, 0, negabin[Quotient[n-1, -2]]*10 + Mod[n, 2]]; Select[Range[0, 2*10^4], And @@ (PalindromeQ /@ {IntegerDigits[#, 2], negabin[#]}) &]
%Y A331894 Intersection of A006995 and A331891.
%Y A331894 Cf. A039724, A095309.
%K A331894 nonn,base
%O A331894 1,3
%A A331894 _Amiram Eldar_, Jan 30 2020