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 A343633 #12 Jun 01 2022 16:59:49 %S A343633 0,1,0,0,0,0,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,1,1,1,-1,-1,-1,-1,-2,0, %T A343633 0,0,0,2,2,2,2,2,1,1,1,1,0,0,0,0,0,0,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2, %U A343633 -2,-2,-2,-1,-1,-1,-1,-1,-1,-1,-1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,0,0,0,0,-2,-2,-2,-2,-3,-2,-2,-2,-2,-2,-2,-2,-2,-1,-1,-1,-1,0 %N A343633 Z-coordinate of the points following the 3D spiral defined in A343630. %C A343633 See the main entry A343630 for details about this 3D generalization of an Ulam type spiral using the Euclidean norm. %C A343633 Sequences A343631 and A343632 give the x and y-coordinates. %C A343633 The sequence can be seen as a table with row lengths A005875, where A005875(r) is the number of points at distance sqrt(r) from the origin. %C A343633 Sequence A343643 is the analog for the square spiral variant A343640. %o A343633 (PARI) d=1; A343633_vec=concat([[P[3] | P<-S=A343630_row(n,d)]+(#S&&!d*=-1) | n<-[0..9]]) \\ the variable d is necessary to correct the z-scan direction in rows between A004215(2k-1) and A004215(2k). %Y A343633 Cf. A343631, A343633 (list of x and z-coordinates). %Y A343633 Cf. A343643 (variant using the sup norm => square spiral). %Y A343633 Cf. A342563 (variant which scans each sphere by increasing z). %Y A343633 Cf. A005875 (number of points on a shell with given radius). %Y A343633 Cf. A004215 (numbers that can't be written as sum of 3 squares => empty shells). %K A343633 sign %O A343633 0,28 %A A343633 _M. F. Hasler_, Apr 28 2021