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A047829 Becomes prime after exactly 10 iterations of f(x) = sum of prime factors of x. 0
167073, 212438, 424876, 480226, 492494, 501219, 567614, 595942, 656714, 668319, 670465, 688958, 723853, 738662, 743973, 768817, 791842, 804558, 849752, 849818, 864074, 887613, 888542, 960452, 975662, 984988, 1012786, 1037845, 1048574 (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

Table of n, a(n) for n=1..29.

MATHEMATICA

spf10Q[n_]:=Boole[PrimeQ[NestList[Total[FactorInteger[#][[All, 1]]]&, n, 10]]] == {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}; Select[Range[105*10^4], spf10Q] (* Harvey P. Dale, Aug 04 2021 *)

CROSSREFS

Sequence in context: A319295 A235846 A187170 * A236494 A236489 A235436

Adjacent sequences:  A047826 A047827 A047828 * A047830 A047831 A047832

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified December 6 11:48 EST 2021. Contains 349563 sequences. (Running on oeis4.)