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A324480
Consider the numbers on the x-axis in the spiral shown in A274641; a(n) is the distance from n to the origin, or -1 if n never appears on the x-axis.
1
0, 1, 1, 2, 2, 3, 4, 3, 7, 6, 4, 5, 8, 10, 5, 6, 7, 11, 8, 12, 14, 10, 18, 9, 9, 13, 12, 20, 21, 24, 11, 22, 13, 14, 16, 17, 15, 15, 17, 18, 19, 36, 16, 23, 26, 23, 21, 27, 19, 27, 28, 20, 22, 25, 24, 43, 29, 47, 50, 25, 26, 37, 43, 49, 34, 28, 42, 52, 53, 30, 30
OFFSET
0,4
COMMENTS
It is conjectured that every nonnegative number appears on the x-axis exactly once.
a(n) is also the distance to the origin from the point n+1 on the x-axis in A274640.
LINKS
EXAMPLE
The portion of the x-axis near 0 is:
... 14 6 5 4 2 0 1 3 7 10 11 ...
and we see that both 1 and 2 are at distance 1 from 0. So a(1) = a(2) = 1.
PROG
(PARI) See Links section.
CROSSREFS
The positive and negative x-axes are given in A274924 and A274928.
Sequence in context: A284199 A284165 A284113 * A164975 A253889 A228754
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 11 2019
EXTENSIONS
More terms from Jinyuan Wang, Feb 27 2020
STATUS
approved