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A047827 Becomes prime after exactly 8 iterations of f(x) = sum of prime factors of x. 1
13682, 18002, 19137, 22934, 24014, 24787, 27364, 27849, 30062, 30993, 32577, 33477, 35410, 35798, 36004, 36398, 36706, 39206, 43333, 43917, 44493, 45219, 45734, 45868, 46142, 46405, 48028, 49546, 50642, 51295, 52413, 53283, 54728 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

f(x) = sum of prime factors without multiplicity, so that f(1500) = 2+3+5 = 10.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..3000

MATHEMATICA

pa8iQ[n_]:=PrimeQ/@NestList[Total[Transpose[FactorInteger[#]][[1]]]&, n, 8] == {False, False, False, False, False, False, False, False, True}; Select[Range[ 55000], pa8iQ] (* Harvey P. Dale, Nov 22 2012 *)

CROSSREFS

Sequence in context: A185471 A203727 A088870 * A204369 A226020 A157669

Adjacent sequences:  A047824 A047825 A047826 * A047828 A047829 A047830

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified August 17 16:21 EDT 2022. Contains 356189 sequences. (Running on oeis4.)