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 A117772 #14 Feb 16 2025 08:33:00
%S A117772 0,1,3,3,5,5,8,8,11,11,18,18,30,30,53,53,93,93,187,187,329,329,600,
%T A117772 600,1080,1080,1936,1936,3657,3657,6756,6756,12328,12328,23127,23127,
%U A117772 43909,43909,83377,83377,156049,156049,295916,295916,570396,570396,1090772
%N A117772 Total number of palindromic primes in base 2 below 2^n.
%C A117772 Every palindrome with an even number of digits is divisible by 11 (in base 2) and therefore is composite (not prime). Hence there is only one palindromic prime with an even number of digits, namely 11_2 = 3_{10}.
%H A117772 Martin Raab, <a href="/A117772/b117772.txt">Table of n, a(n) for n = 1..66</a>
%H A117772 Eric Weisstein: <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>.
%Y A117772 Cf. A016041, A117697.
%K A117772 nonn,base
%O A117772 1,3
%A A117772 _Martin Renner_, Apr 15 2006
%E A117772 a(23)-a(40) from _Donovan Johnson_, Dec 02 2009
%E A117772 Extended to a(66) by _Martin Raab_, Oct 20 2015