A047829 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A047829

Becomes prime after exactly 10 iterations of f(x) = sum of prime factors of x.

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