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A331954
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a(n) is the least positive k such that floor(n/k) is a prime number.
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3
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1, 1, 2, 1, 2, 1, 3, 3, 2, 1, 4, 1, 2, 2, 3, 1, 5, 1, 4, 3, 2, 1, 7, 5, 2, 2, 4, 1, 4, 1, 6, 3, 2, 2, 5, 1, 2, 2, 3, 1, 6, 1, 4, 4, 2, 1, 9, 7, 7, 3, 3, 1, 4, 4, 5, 3, 2, 1, 8, 1, 2, 2, 9, 5, 5, 1, 4, 3, 3, 1, 10, 1, 2, 2, 4, 4, 4, 1, 6, 6, 2, 1, 11, 5, 2, 2
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OFFSET
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2,3
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COMMENTS
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This sequence is unbounded; a(n!*p^2) > n where n > 1 and p is a prime number > n.
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LINKS
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FORMULA
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a(n) = 1 iff n is a prime number.
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EXAMPLE
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For n = 8:
- floor(8/1) = 8 is not a prime number,
- floor(8/2) = 4 is not a prime number,
- floor(8/3) = 2 is a prime number,
- hence a(8) = 3.
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MATHEMATICA
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Array[Block[{k = 1}, While[! PrimeQ@ Floor[#/k], k++]; k] &, 86, 2] (* Michael De Vlieger, Feb 04 2020 *)
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PROG
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(PARI) a(n) = for (k=1, oo, if (isprime(n\k), return (k)))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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