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A166061
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19-rough numbers: positive integers that have no prime factors less than 19.
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11
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1, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271
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OFFSET
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1,2
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COMMENTS
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Or, positive integers relatively prime to 510510 = 2*3*5*7*11*13*17.
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LINKS
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FORMULA
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a(n) = k*n + O(1) where k = 17017/3072 = 5.539388.... In particular, k*n - 31 < a(n) < k*n + 25. - Charles R Greathouse IV, Sep 24 2018
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EXAMPLE
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437 = 19 * 23 is in the sequence since the two prime factors, 19 and 23, are not less than 19.
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MATHEMATICA
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Join[{1}, Select[Range[300], Min[Transpose[FactorInteger[#]][[1]]]>18&]] (* Harvey P. Dale, Feb 18 2015 *)
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PROG
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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