A047827 Becomes prime after exactly 8 iterations of f(x) = sum of prime factors of x.

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

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