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A354856
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a(1) = 1, a(n) = the number of times a(n-1) appears among the first n-2 terms.
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0
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1, 0, 0, 1, 1, 2, 0, 2, 1, 3, 0, 3, 1, 4, 0, 4, 1, 5, 0, 5, 1, 6, 0, 6, 1, 7, 0, 7, 1, 8, 0, 8, 1, 9, 0, 9, 1, 10, 0, 10, 1, 11, 0, 11, 1, 12, 0, 12, 1, 13, 0, 13, 1, 14, 0, 14, 1, 15, 0, 15, 1, 16, 0, 16, 1, 17, 0, 17, 1, 18, 0, 18, 1, 19, 0, 19, 1, 20, 0, 20
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OFFSET
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1,6
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LINKS
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FORMULA
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EXAMPLE
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a(10) = 3 because a(9) = 1 and 3 other 1s appear before that.
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PROG
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(Python)
from collections import Counter
from itertools import count, islice
def agen(): # generator of terms
anprev, an, inventory = None, 1, Counter()
for n in count(2):
yield an
anprev, an = an, inventory[an]
inventory[anprev] += 1
(PARI) lista(nn) = my(va=vector(nn)); va[1] = 1; for (n=2, nn, my(vb = vector(n-2, k, va[k])); va[n] = #select(x->(x==va[n-1]), vb); ); va; \\ Michel Marcus, Jun 13 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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