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A199769
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Number of brackets in distinct sets with fewest possible elements
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1
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1, 2, 3, 4, 4, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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There are three repetitions of 5 because of the sets {{{{{}}}}}, {{{}, {{}}}}, and {{{{}}}, {}}.
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MAPLE
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b:= proc(n) a(n):= `if`(n<2, n, add(a(n-k)*add(b(d)*d*
(-1)^(k/d+1), d=numtheory[divisors](k)), k=1..n-1)/(n-1))
end:
T:= n-> n$b(n):
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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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