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 A117776 #9 Feb 16 2025 08:33:00 %S A117776 1,0,2,0,3,0,12,0,8,0,47,0,106,0,280,0,720,0,1825,0,5107,0,14072,0, %T A117776 38606,0,107852,0,301048,0,852975,0,2369097,0,6699177,0,19111621,0, %U A117776 54510099,0,155404674,0 %N A117776 Total number of palindromic primes in base 3 with n digits. %C A117776 Every palindrome with an even number of digits is divisible by 11 (in base 3) and therefore is composite (not prime). Hence there is no palindromic prime with an even number of digits. %H A117776 Eric Weisstein: <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>. %Y A117776 Cf. A029971, A117698. %K A117776 nonn,base %O A117776 1,3 %A A117776 _Martin Renner_, Apr 15 2006 %E A117776 a(15)-a(42) from _Chai Wah Wu_, Dec 27 2015