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 A117777 #10 Feb 16 2025 08:33:00 %S A117777 2,3,6,6,16,16,45,45,142,142,435,435,1417,1417,4802,4802,16433,16433, %T A117777 57808,57808,210708,210708,752233,752233,2748264,2748264,10211513, %U A117777 10211513,38013234,38013234,140417288,140417288 %N A117777 Total number of palindromic primes in base 4 below 4^n. %C A117777 Every palindrome with an even number of digits is divisible by 11 (in base 4) and therefore is composite (not prime). Hence there is only one palindromic prime with an even number of digits. %H A117777 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>. %Y A117777 Partial sums of A117778. %Y A117777 Cf. A029972, A117699. %Y A117777 Cf. A117772, A117775, A117779, A117781, A117783, A117785, A117787. %K A117777 nonn,base,more %O A117777 1,1 %A A117777 _Martin Renner_, Apr 15 2006 %E A117777 a(13)-a(32) from the data at A117778 added by _Amiram Eldar_, Mar 21 2021