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 A145825 #4 Jul 22 2025 06:13:54 %S A145825 1,5,1,5,17,21,17,21,1,5,1,5,17,21,17,21,65,69,65,69,81,85,81,85,65, %T A145825 69,65,69 %N A145825 a(n) is in A145818 such that (4n-1-a(n))/2 is in A145818 as well. %C A145825 Note that a(4n)=a(4n-2), a(4n-1)=a(4n-3). %Y A145825 A145818 A145812 A145819 A145822 %K A145825 nonn %O A145825 1,2 %A A145825 _Vladimir Shevelev_, Oct 20 2008