OFFSET
1,3
COMMENTS
The terms corresponding to the corner points of the spiral with a(k-1) < a(k) > a(k+1), i.e., 2, 2, 2, 5, 8, 8, 8, 13, 18, 18, 18, ... are given by the sequence A001105(1) repeated 3 times, (A001105(1)+A001105(2))/2, A001105(2) repeated 3 times, (A001105(2)+A001105(3))/2, A001105(3) repeated 3 times, ... .
These numbers are the norms of the Gaussian integers discussed in A345436. - N. J. A. Sloane, Jun 25 2021
LINKS
Hugo Pfoertner, Table of n, a(n) for n = 1..10000
N. J. A. Sloane, Sketch showing first 49 cells (numbered in black, starting at 0) of the square spiral and the corresponding squared distances from the origin (red). (This illustration assumes the sequence has offset 0.)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Hugo Pfoertner, Jul 18 2020
STATUS
approved