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A136023
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The largest prime factor among all composites <= 10^n.
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1
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5, 47, 499, 4999, 49999, 499979, 4999999, 49999991, 499999993, 4999999937, 49999999967, 499999999979, 4999999999937, 49999999999981, 499999999999999, 4999999999999997, 49999999999999993, 499999999999999931, 4999999999999999963, 49999999999999999951
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| This is the largest single divisor contributing to A136021(n).
If 4 concatenated with n-1 nines is prime, it will be the largest factor. This candidate does not work for n=6 because 499999 is not prime.
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EXAMPLE
| a(3)=499 because it is the largest prime factor of all k<=10^3; the largest k in that interval with this factor is k=2*499 = 998.
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CROSSREFS
| Cf. A136021, A052369.
Sequence in context: A181582 A124267 A124450 * A074192 A058806 A006902
Adjacent sequences: A136020 A136021 A136022 * A136024 A136025 A136026
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KEYWORD
| nonn
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Dec 12 2007
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EXTENSIONS
| Edited and more terms added by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 17 2009
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