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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. 0

%I

%S 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

%N 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.

%C It is conjectured that every nonnegative number appears on the x-axis exactly once.

%C a(n) is also the distance to the origin from the point n+1 on the x-axis in A274640.

%C Needs a large b-file: it will be interesting to see how irregular this sequence is.

%e The portion of the x-axis near 0 is:

%e ... 14 6 5 4 2 0 1 3 7 10 11 ...

%e and we see that both 1 and 2 are at distance 1 from 0. So a(1) = a(2) = 1.

%Y Cf. A274640, A274641.

%Y The positive and negative x-axes are given in A274924 and A274928.

%K nonn,more

%O 0,4

%A _N. J. A. Sloane_, Mar 11 2019

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Last modified September 18 12:00 EDT 2019. Contains 327170 sequences. (Running on oeis4.)