A324481 Index of first occurrence of n in the spiral shown in A274641.

0, 1, 2, 3, 7, 8, 26, 27, 30, 34, 35, 48, 55, 62, 63, 80, 101, 119, 130, 131, 155, 180, 210, 224, 253, 254, 271, 303, 305, 321, 322, 323, 419, 483, 504, 505, 568, 571, 573, 624, 649, 650, 728, 755, 810, 812, 840, 898, 953, 954, 956, 957, 959, 960, 1189

Offset: 0

Author

N. J. A. Sloane, Mar 11 2019

Keywords

• nonn

Comments

Also index of first occurrence of n+1 in the spiral shown in A274640.

Links

• N. J. A. Sloane, Table of n, a(n) for n = 0..223

Crossrefs

Cf. A274640, A274641.

Programs

Python

A324481 = lambda n: next(i for i,a in enumerate(A274640()) if a==n+1) # slow

Python

def A324481(): # generator of the sequence
   n=1
   for i,a in enumerate(A274640()):
      if a==n: yield i; n += 1
[a for a,A324481(),range(99))%5D%20%23%20_M.%20F.%20Hasler"> in zip(A324481(),range(99))] # _M. F. Hasler, Feb 01 2025

Formula

Conjecture: a(n) = c(n)*n^2 with 0.32 <= c(n) <= 1 for all n, maybe lim c(n) ~ 0.4. - M. F. Hasler, Feb 01 2025