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 A331892 #10 Jan 31 2020 04:16:08 %S A331892 1,5,7,17,21,31,35,57,65,85,93,119,127,147,155,201,217,257,273,325, %T A331892 341,381,397,455,471,511,527,579,595,635,651,745,777,857,889,993,1025, %U A331892 1105,1137,1253,1285,1365,1397,1501,1533,1613,1645,1767,1799,1879,1911,2015 %N A331892 Positive numbers k such that the negabinary expansion (A039724) of -k is palindromic. %C A331892 Numbers of the form 2^(2*m-1) - 1 (A083420) and 2^(2*m) + 1 (A052539) are terms. %H A331892 Amiram Eldar, <a href="/A331892/b331892.txt">Table of n, a(n) for n = 1..10000</a> %e A331892 5 is a term since the negabinary representation of -5 is 1111 which is palindromic. %t A331892 negabin[n_] := negabin[n] = If[n==0, 0, negabin[Quotient[n-1, -2]]*10 + Mod[n, 2]]; Select[Range[2000], PalindromeQ @ negabin[-#] &] %Y A331892 Cf. A002113, A005352, A006995, A014190, A039724, A094202, A212529, A331191, A331891. %K A331892 nonn,base %O A331892 1,2 %A A331892 _Amiram Eldar_, Jan 30 2020