A343642 - OEIS

%I #8 May 06 2021 22:09:13

%S 0,0,0,1,1,1,0,-1,-1,-1,0,1,1,1,0,-1,-1,-1,0,1,1,1,0,-1,-1,-1,0,0,0,1,

%T 1,1,0,-1,-1,-1,0,1,2,2,2,2,2,1,0,-1,-2,-2,-2,-2,-2,-1,0,1,2,2,2,2,2,

%U 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,-1,-2,-2,-2,-2,-2,-1,0,1,2,2,2,2,2,1,0

%N Y-coordinate of points following the 3D square spiral defined in A343640.

%C See A343640 for more information 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="/A343642/b343642.txt">Table of n, a(n) for n = 0..9260</a>

%o (PARI) A343642_vec=concat([[P[2]| P<-A343640_row(n)] | n<-[0..2]]) \\ From 0 up to n there are (2n+1)^3 points with 3 coordinates each.

%Y Cf. A343641, A343643 (list of x and z-coordinates).

%Y Cf. A343632 (variant using the Euclidean norm), A342562 (another variant).

%Y Cf. A010014 (number of points on a shell with given radius => row lengths).

%K sign,look,tabf

%O 0,39

%A _M. F. Hasler_, Apr 28 2021