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A375094
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a(n) is the least number not occurring in a Collatz trajectory of n steps.
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2
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2, 3, 3, 3, 3, 3, 3, 6, 7, 7, 7, 7, 7, 7, 7, 7, 9, 9, 9, 18, 25, 25, 25, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27
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OFFSET
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0,1
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COMMENTS
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LINKS
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EXAMPLE
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a(5) = 3 because there are two trajectories with 5 steps, namely (32,16,8,4,2,1) and (5,16,8,4,2,1). 3 is the smallest number not appearing in both.
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PROG
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(Python)
# output in b-file format
from itertools import count
n = 0
for k in count():
m = k
s = 0
while m > 1:
m = m // 2 if m % 2 == 0 else 3*m+1
s += 1
while n < s:
print(n, k, flush=True)
n += 1
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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