%I #11 May 07 2021 00:44:42
%S 0,0,1,1,0,-1,-1,-1,0,1,1,1,0,-1,-1,-1,0,1,1,1,0,-1,-1,-1,0,1,0,0,1,1,
%T 0,-1,-1,-1,0,1,2,2,2,1,0,-1,-2,-2,-2,-2,-2,-1,0,1,2,2,2,2,2,1,0,-1,
%U -2,-2,-2,-2,-2,-1,0,1,2,2,2,2,2,1,0,-1,-2,-2,-2,-2,-2,-1,0,1,2,2,2,2,2,1,0,-1,-2,-2,-2,-2,-2,-1,0
%N X-coordinate of points following the 3D square spiral defined in A343640.
%C See A343640 for more about this 3D generalization of the 2D Ulam type square spiral.
%C The sequence can be seen as a table with row lengths A010014, where A010014(r) is the number of points of Z^3 with sup-norm r.
%H Hugo Pfoertner, <a href="/A343641/b343641.txt">Table of n, a(n) for n = 0..9260</a>
%o (PARI) A343641_vec=concat([[P[1]| P<-A343640_row(r)] | r<-[0..2]]) \\ From r=0 up to n there are (2n+1)^3 points with 3 coordinates each.
%Y Cf. A343640 (triples), A343642 and A343643 (list of y and z-coordinates).
%Y Cf. A343631 (variant using the Euclidean norm), A342561 (another variant).
%Y Cf. A010014 (number of points on a shell with given radius => row lengths).
%K sign,tabf
%O 0,37
%A _M. F. Hasler_, Apr 28 2021