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 A117781 #10 Feb 16 2025 08:33:00 %S A117781 3,4,10,10,31,31,126,126,571,571,2752,2752,14248,14248,73971,73971, %T A117781 389920,389920,2108414,2108414,11512078,11512078 %N A117781 Total number of palindromic primes in base 6 below 6^n. %C A117781 Every palindrome with an even number of digits is divisible by 11 (in base 6) and therefore is composite (not prime). Hence there is only one palindromic prime with an even number of digits. %H A117781 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>. %Y A117781 Partial sums of A117782. %Y A117781 Cf. A029974, A117701. %Y A117781 Cf. A117772, A117775, A117777, A117779, A117783, A117785, A117787. %K A117781 nonn,base,more %O A117781 1,1 %A A117781 _Martin Renner_, Apr 15 2006 %E A117781 a(11)-a(22) from the data at A117782 added by _Amiram Eldar_, Mar 21 2021