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A048133
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Least number which becomes prime or 4 after exactly n iterations of f(x) = sum of prime factors of x.
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2
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2, 6, 8, 14, 26, 62, 134, 393, 1257, 4659, 9314, 27933, 167073, 334142, 4677862, 14033577, 56134292, 2133102298, 11788191218, 52541651594
(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 with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22.
Identical to the different-offset A121360 except for the second term. - Hans Havermann, Oct 05 2010
a(20) <= 536226160966. a(21) <= 2681130804805. a(22) <= 8512643845707. - Donovan Johnson
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CROSSREFS
| Sequence in context: A187217 A022112 A107019 * A199697 A135619 A067795
Adjacent sequences: A048130 A048131 A048132 * A048134 A048135 A048136
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
| a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 25 2010
Edited comment and a(18)-a(19) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 16 2010
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