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A047830
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Least number which becomes prime after exactly n iterations of f(x) = sum of prime factors of x.
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0
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2, 4, 14, 26, 62, 134, 393, 1774, 13682, 41037, 167073, 334142, 4677862, 14033577, 79464886, 476789307, 3488435822, 34884358195
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| f(x) = sum of prime factors without multiplicity, so that f(1500) = 2+3+5 = 10.
a(18) <= 148005789513. a(19) <= 1603226096774. a(20) <= 16032260967715. - Donovan Johnson
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CROSSREFS
| Sequence in context: A102930 A135113 A050564 * A036051 A115626 A116021
Adjacent sequences: A047827 A047828 A047829 * A047831 A047832 A047833
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
| a(14)-a(15) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 13 2009
Edited comment and a(16)-a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 16 2010
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