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 A321473 #9 Jun 22 2020 12:24:59 %S A321473 0,1,2,3,4,6,8,9,10,12,13,16,18,20,23,24,26,27,28,30,31,34,36,37,39, %T A321473 40,46,48,52,54,56,59,60,62,65,68,69,72,74,78,80,81,82,84,85,88,90,91, %U A321473 93,94,100,102,106,108,109,111,112,117,118,120,121,130,136,138 %N A321473 Nonnegative numbers whose nonzero digits in ternary expansion are palindromic. %C A321473 This sequence corresponds to the fixed points of A321464, and contains A014190. %H A321473 Harvey P. Dale, <a href="/A321473/b321473.txt">Table of n, a(n) for n = 1..1000</a> %e A321473 For n = 1594426: %e A321473 - the ternary expansion of 1594426 is "10000000010211", %e A321473 - the corresponding nonzero digits are "11211", which are palindromic, %e A321473 - hence 1594426 belongs to the sequence. %t A321473 Select[Range[0,200],PalindromeQ[FromDigits[IntegerDigits[#,3]/.(0-> Nothing)]]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jun 22 2020 *) %o A321473 (PARI) is(n, base=3) = my (t=select(sign, digits(n, base))); t==Vecrev(t) %Y A321473 Cf. A014190, A321464. %K A321473 nonn,base %O A321473 1,3 %A A321473 _Rémy Sigrist_, Nov 11 2018