%I #10 Feb 01 2025 23:15:15
%S 0,1,2,3,7,8,26,27,30,34,35,48,55,62,63,80,101,119,130,131,155,180,
%T 210,224,253,254,271,303,305,321,322,323,419,483,504,505,568,571,573,
%U 624,649,650,728,755,810,812,840,898,953,954,956,957,959,960,1189
%N Index of first occurrence of n in the spiral shown in A274641.
%C Also index of first occurrence of n+1 in the spiral shown in A274640.
%H N. J. A. Sloane, <a href="/A324481/b324481.txt">Table of n, a(n) for n = 0..223</a>
%F 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
%o (Python) A324481 = lambda n: next(i for i,a in enumerate(A274640()) if a==n+1) # slow
%o (Python)
%o def A324481(): # generator of the sequence
%o n=1
%o for i,a in enumerate(A274640()):
%o if a==n: yield i; n += 1
%o [a for a,_ in zip(A324481(),range(99))] # _M. F. Hasler_, Feb 01 2025
%Y Cf. A274640, A274641.
%K nonn,changed
%O 0,3
%A _N. J. A. Sloane_, Mar 11 2019