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 A048704 #12 May 27 2024 07:14:30 %S A048704 0,1,2,3,13,17,21,25,26,30,34,38,39,43,47,51,205,221,237,253,257,273, %T A048704 289,305,309,325,341,357,361,377,393,409,410,426,442,458,462,478,494, %U A048704 510,514,530,546,562,566,582,598,614,615,631,647,663,667,683,699,715,719 %N A048704 Base 4 palindromes of even length divided by 5. a(n) = A048703(n)/5. %H A048704 Amiram Eldar, <a href="/A048704/b048704.txt">Table of n, a(n) for n = 0..10000</a> %t A048704 q[n_] := EvenQ[IntegerLength[5*n, 4]] && PalindromeQ[IntegerDigits[5*n, 4]]; Select[Range[0, 1000], q] (* _Amiram Eldar_, May 27 2024 *) %Y A048704 Cf. A048702 (base 2 palindromes of even length divided by 3), A048703. %K A048704 nonn,base %O A048704 0,3 %A A048704 _Antti Karttunen_, Mar 07 1999 %E A048704 More terms from _Amiram Eldar_, May 27 2024