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 A029986 #23 Feb 10 2025 19:56:40 %S A029986 0,1,5,17,21,65,71,83,257,273,281,317,1025,1055,4097,4161,4193,4401, %T A029986 5157,5179,5221,16385,16511,16865,17239,65537,65793,65921,66753,68695, %U A029986 69521,69777,80739,82053,82171,82309,82885,83301,262145 %N A029986 Numbers k such that k^2 is palindromic in base 4. %H A029986 Seiichi Manyama, <a href="/A029986/b029986.txt">Table of n, a(n) for n = 1..100</a> %H A029986 Patrick De Geest, <a href="https://www.worldofnumbers.com/nobase10pg2.htm">Palindromic Squares in bases 2 to 17</a> %t A029986 Select[Range[0,300000],IntegerDigits[#^2,4]==Reverse[ IntegerDigits[ #^2,4]]&] (* _Harvey P. Dale_, Dec 01 2015 *) %o A029986 (PARI) isok(k) = my(d=digits(k^2,4)); d == Vecrev(d); \\ _Michel Marcus_, Jul 04 2021 %Y A029986 Cf. A007090, A014192. %Y A029986 Numbers k such that k^2 is palindromic in base b: A003166 (b=2), A029984 (b=3), this sequence (b=4), A029988 (b=5), A029990 (b=6), A029992 (b=7), A029805 (b=8), A029994 (b=9), A002778 (b=10), A029996 (b=11), A029737 (b=12), A029998 (b=13), A030072 (b=14), A030073 (b=15), A029733 (b=16), A118651 (b=17). %K A029986 nonn,base %O A029986 1,3 %A A029986 _Patrick De Geest_