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 A354885 #18 Jun 16 2022 02:33:48
%S A354885 0,1,4,10,13,16,28,40,52,82,91,112,121,160,244,280,328,364,484,730,
%T A354885 757,820,847,976,1003,1066,1093,1312,1456,2188,2296,2440,2548,2920,
%U A354885 3028,3172,3280,3904,4372,6562,6643,6832,6913,7300,7381,7570,7651,8752,8833,9022
%N A354885 Numbers that are palindromes in both ternary and balanced ternary representations.
%H A354885 Amiram Eldar, <a href="/A354885/b354885.txt">Table of n, a(n) for n = 1..10000</a>
%e A354885 4 is a term since its ternary and balanced ternary representation are both 11 which is a palindrome.
%e A354885 16 is a term since its ternary representation is 121 and its balanced ternary representation (with 2 standing for the -1 digit) is 1221, and both are palindromes.
%t A354885 Select[Range[0, 10^4], PalindromeQ[IntegerDigits[#, 3]] && PalindromeQ @ balTernDigits[#] &] (* using balTernDigits by _Robert G. Wilson v_ at A134027 *)
%o A354885 (PARI) is(n) = {my (t=digits(n,3)); if (t==Vecrev(t), my (b=[], d); while (n, b=concat(d=[0,1,-1][1+n%3], b); n=(n-d)/3); b==Vecrev(b), 0)} \\ _Rémy Sigrist_, Jun 10 2022
%Y A354885 Intersection of A014190 and A134027.
%Y A354885 Subsequences: A003462, A034472 \ {2}, A354886.
%Y A354885 Cf. A007089, A140267.
%K A354885 nonn,base
%O A354885 1,3
%A A354885 _Amiram Eldar_, Jun 10 2022