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 A331893 #10 Jan 31 2020 04:16:00
%S A331893 1,5,7,17,21,31,57,65,85,127,155,217,257,273,325,341,455,511,635,857,
%T A331893 889,993,1025,1105,1253,1285,1365,1799,2047,2159,2555,2667,3417,3577,
%U A331893 3641,3937,4097,4161,4369,4433,4965,5125,5189,5397,5461,6951,7175,7967,8191
%N A331893 Positive numbers k such that both k and -k are a palindromes in negabinary representation.
%C A331893 Numbers of the form 2^(2*m-1) - 1 (A083420) and 2^(2*m) + 1 (A052539) are terms.
%H A331893 Amiram Eldar, <a href="/A331893/b331893.txt">Table of n, a(n) for n = 1..10000</a>
%e A331893 5 is a term since the negabinary representation of 5, 101, and the negabinary representation of -5, 1111, are both palindromic.
%t A331893 negabin[n_] := negabin[n] = If[n==0, 0, negabin[Quotient[n-1, -2]]*10 + Mod[n, 2]]; nbPalinQ[n_] := And @@ (PalindromeQ @ negabin[#] & /@ {n, -n}); Select[Range[2^13], nbPalinQ]
%Y A331893 Intersection of A331891 and A331892.
%Y A331893 Cf. A005352, A039724, A212529.
%K A331893 nonn,base
%O A331893 1,2
%A A331893 _Amiram Eldar_, Jan 30 2020