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 A029988 #20 Feb 10 2025 21:40:06
%S A029988 0,1,2,6,26,31,66,126,156,626,651,756,804,3126,3276,3756,9054,15626,
%T A029988 15751,16276,18434,18756,32578,34162,46704,78126,78876,81276,93756,
%U A029988 390626,391251,393876,406276,468756,487981,1166454,1953126,1956876
%N A029988 Numbers k such that k^2 is palindromic in base 5.
%H A029988 Patrick De Geest, <a href="https://www.worldofnumbers.com/nobase10pg2.htm">Palindromic Squares in bases 2 to 17</a>
%H A029988 G. J. Simmons, <a href="/A002778/a002778.pdf">On palindromic squares of non-palindromic numbers</a>, J. Rec. Math., 5 (No. 1, 1972), 11-19. [Annotated scanned copy]
%t A029988 pal5Q[n_]:=Module[{idn5=IntegerDigits[n^2,5]},idn5==Reverse[idn5]]; Select[ Range[ 0,2*10^6],pal5Q] (* _Harvey P. Dale_, Feb 02 2023 *)
%Y A029988 Cf. A002778, A003166, A007091, A263611, A263612, A029989.
%K A029988 nonn,base
%O A029988 1,3
%A A029988 _Patrick De Geest_