%I #10 Nov 14 2022 10:00:21

%S 1,3,6,9,25,21,17,109,198,67,860,114,148,261,57,137,82,37,52,215,447,

%T 43,105,404,267,163,414,94,154,1292,184,716,142,669,243,73,1685,126,

%U 360,209,329,324,355,88,542,300,887,366,422,492,1053,1754,256,941,946,711,679,178,283,3273,2221,225

%N The index of A358402 where n first appears, or 0 if n never appears.

%C See A358402 for further details.

%o (Python)

%o from itertools import count, islice

%o def agen():

%o k, an, first, prev = 0, 0, {0: 1}, {0: 1}

%o for n in count(2):

%o while k in first: yield first[k]; k += 1

%o an1 = 0 if first[an] == n-1 else min(n-1-prev[an], first[an])

%o if an1 not in first: first[an1] = prev[an1] = n

%o prev[an] = n-1

%o an = an1

%o print(list(islice(agen(), 62))) # _Michael S. Branicky_, Nov 14 2022

%Y Cf. A358402, A358405, A358406, A181391.

%K nonn

%O 0,2

%A _Scott R. Shannon_, Nov 14 2022