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 A163258 #9 Jan 05 2025 19:51:39 %S A163258 1,2,3,4,1,2,5,3,6,4,1,2,7,5,3,8,6,4,1,2,9,7,5,3,10,8,6,4,1,2,11,9,7, %T A163258 5,3,12,10,8,6,4,1,2,13,11,9,7,5,3,14,12,10,8,6,4,1,2,15,13,11,9,7,5, %U A163258 3,16,14,12,10,8,6,4,1,2,17,15,13,11,9,7,5,3,18,16,14,12,10,8,6,4 %N A163258 Fractal sequence of the interspersion A163257. %C A163258 As a fractal sequence, A163258 contains every positive integer; indeed, A163258 properly contains itself (infinitely many times). %H A163258 Clark Kimberling, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Papers1/48-1/Kimberling.pdf">Doubly interspersed sequences, double interspersions and fractal sequences</a>, The Fibonacci Quarterly 48 (2010) 13-20. %e A163258 Append the following segments: %e A163258 1 2 3 4 %e A163258 1 2 5 3 6 4 %e A163258 1 2 7 5 3 8 6 4 %e A163258 1 2 9 7 5 3 10 8 6 4 %e A163258 For n>1, the n-th segment arises from the (n-1)st by inserting 2*n+1 at position 3 and 2*n+2 at position n+3. %Y A163258 Cf. A163253, A163254, A163255, A163256, A163258. %K A163258 nonn %O A163258 1,2 %A A163258 _Clark Kimberling_, Jul 24 2009