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 A334220 #15 May 06 2025 11:19:49 %S A334220 0,1,2,3,3,3,4,4,4,5,6,7,7,7,7,6,6,6,5,5,5,5,6,7,7,7,8,8,8,9,10,10,10, %T A334220 10,9,9,9,8,8,8,8,9,10,11,11,11,12,12,12,13,14,15,15,15,15,14,14,14, %U A334220 13,13,13,13,14,15,15,15,15,14,14,14,13,13,13,12,12 %N A334220 a(n) is the X-coordinate of the point at n steps forward from the origin along the space filling curve U defined in A334188; sequence A334221 gives Y-coordinates. %H A334220 Rémy Sigrist, <a href="/A334220/b334220.txt">Table of n, a(n) for n = 0..8066</a> %H A334220 Rémy Sigrist, <a href="/A334220/a334220.gp.txt">PARI program for A334220</a> %H A334220 <a href="/index/Con#coordinates_2D_curves">Index entries for sequences related to coordinates of 2D curves</a> %F A334220 A334188(A334221(n), a(n)) = n. %e A334220 The "forward" branch of curve U starting from the origin is as follows: %e A334220 | %e A334220 6| 25.. %e A334220 | | %e A334220 5| 24 %e A334220 | | %e A334220 4| 21...22...23 %e A334220 | | %e A334220 3| 20 15...14 %e A334220 | | | | %e A334220 2| 5....6 19 16 13 %e A334220 | | | | | | %e A334220 1| 4 7 18...17 12 %e A334220 | | | | %e A334220 0| 0....1....2....3 8....9...10...11 %e A334220 ---+---------------------------------------- %e A334220 y/x| 0 1 2 3 4 5 6 7 %e A334220 - hence a(10) = a(15) = a(16) = a(17) = a(22) = 6. %o A334220 (PARI) See Links section. %Y A334220 Cf. A334188, A334221. %K A334220 nonn,look %O A334220 0,3 %A A334220 _Rémy Sigrist_, Apr 19 2020