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 A117698 #8 Feb 16 2025 08:33:00 %S A117698 2,111,212,12121,20102,22122,1001001,1021201,1111111,1201021,1221221, %T A117698 2001002,2021202,2101012,2111112,2121212,2201022,2211122,102111201, %U A117698 110111011 %N A117698 Palindromic primes in base 3 (written in base 3). %H A117698 R. J. Mathar, <a href="/A117698/b117698.txt">Table of n, a(n) for n = 1..179</a> %H A117698 Eric Weisstein: <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>. %Y A117698 Cf. A029971. %K A117698 nonn,base %O A117698 1,1 %A A117698 _Martin Renner_, Apr 13 2006