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 A305259 #17 Jun 05 2018 10:04:55 %S A305259 1,0,-1,0,2,1,0,-1,-2,-1,0,1,3,2,1,0,-1,-2,-3,-2,-1,0,1,2,4,3,2,1,0, %T A305259 -1,-2,-3,-4,-3,-2,-1,0,1,2,3,5,4,3,2,1,0,-1,-2,-3,-4,-5,-4,-3,-2,-1, %U A305259 0,1,2,3,4,6,5,4,3,2,1,0,-1,-2,-3,-4,-5,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5 %N A305259 x-coordinates of a point moving counterclockwise on concentric squares of grid points rotated by Pi/4 with side length m*sqrt(2), m=1,2,..., with jump to next square on the positive x-axis. %C A305259 The corresponding y-coordinates of the point are given in A010751. %H A305259 Hugo Pfoertner, <a href="/A305259/a305259.pdf">Illustration of A010751(n+1) vs A305259(n)</a>. %e A305259 y ^ %e A305259 | | %e A305259 3 | 16 28 %e A305259 | / | \ \ %e A305259 | / | \ \ %e A305259 | / | \ \ %e A305259 2 | 17 7 15 27 %e A305259 | / / | \ \ \ %e A305259 | / / | \ \ \ %e A305259 | / / | \ \ \ %e A305259 1 | 18 8 2 6 14 26 %e A305259 | / / / | \ \ \ \ %e A305259 | / / / | \ \ \ \ %e A305259 | / / / | \ \ \ \ %e A305259 0 +-19------9------3------+------1------5-----13-----25-> %e A305259 | \ \ \ | --------/ / / %e A305259 | \ \ \ | / ---------- / %e A305259 | \ \ \ | / / ---------- %e A305259 -1 | 20 10 4 12 24 %e A305259 | \ \ | / / %e A305259 | \ \ | / / %e A305259 | \ \ | / / %e A305259 -2 | 21 11 23 %e A305259 | \ | / %e A305259 | \ | / %e A305259 | \ | / %e A305259 -3 | 22 %e A305259 | | %e A305259 +-----------------------+---------------------------> %e A305259 -3 -2 -1 0 1 2 3 x %o A305259 (PARI) for(m=1,6,vert=[m,0,-m,0,m];for(k=1,4,v=vert[k];w=vert[k+1];s=sign(w-v);forstep(j=v,w-s,s,print1(j,", ")))) \\ _Hugo Pfoertner_, Jun 02 2018 %Y A305259 Cf. A001844 (jump to next square), A010751 (y-coordinates), A304587. %K A305259 sign %O A305259 1,5 %A A305259 _Hugo Pfoertner_, Jun 02 2018