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 A334221 #14 May 06 2025 11:19:59 %S A334221 0,0,0,0,1,2,2,1,0,0,0,0,1,2,3,3,2,1,1,2,3,4,4,4,5,6,6,5,4,4,4,3,2,1, %T A334221 1,2,3,3,2,1,0,0,0,0,1,2,2,1,0,0,0,0,1,2,3,3,2,1,1,2,3,4,4,4,5,6,7,7, %U A334221 6,5,5,6,7,7,6,5,4,3,3,4,5,6,7,7,6,5,5 %N A334221 a(n) is the Y-coordinate of the point at n steps forward from the origin along the space filling curve U defined in A334188; sequence A334220 gives X-coordinates. %H A334221 Rémy Sigrist, <a href="/A334221/b334221.txt">Table of n, a(n) for n = 0..8066</a> %H A334221 Rémy Sigrist, <a href="/A334221/a334221.gp.txt">PARI program for A334221</a> %H A334221 <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a> %F A334221 A334188(a(n), A334220(n)) = n. %e A334221 The "forward" branch of curve U starting from the origin is as follows: %e A334221 | %e A334221 6| 25.. %e A334221 | | %e A334221 5| 24 %e A334221 | | %e A334221 4| 21...22...23 %e A334221 | | %e A334221 3| 20 15...14 %e A334221 | | | | %e A334221 2| 5....6 19 16 13 %e A334221 | | | | | | %e A334221 1| 4 7 18...17 12 %e A334221 | | | | %e A334221 0| 0....1....2....3 8....9...10...11 %e A334221 ---+---------------------------------------- %e A334221 y/x| 0 1 2 3 4 5 6 7 %e A334221 - hence a(5) = a(6) = a(13) = a(16) = a(19) = 2. %o A334221 (PARI) See Links section. %Y A334221 Cf. A334188, A334220. %K A334221 nonn,look %O A334221 0,6 %A A334221 _Rémy Sigrist_, Apr 19 2020