The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A048131 Becomes prime or 4 after exactly 9 iterations of f(x) = sum of prime factors of x. 1
 4659, 5294, 5937, 9286, 10334, 10843, 15490, 16382, 17972, 18201, 18588, 18735, 19137, 19984, 20059, 22482, 23073, 23806, 25405, 26405, 26547, 27622, 27845, 28694, 28772, 30062, 30486, 31686, 32156, 32313, 33177, 33238, 33414, 33944 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS f(x) = sum of prime factors with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22. LINKS Table of n, a(n) for n=1..34. MATHEMATICA sopf[n_]:=Total[Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[n]]]; nifQ[ n_]:=Length[NestWhileList[sopf, n, !PrimeQ[#]&&#!=4&]]==10; Select[ Range[ 4000, 34000], nifQ] (* Harvey P. Dale, Sep 06 2021 *) CROSSREFS Sequence in context: A069646 A159220 A020422 * A062626 A204489 A252127 Adjacent sequences: A048128 A048129 A048130 * A048132 A048133 A048134 KEYWORD nonn AUTHOR David W. Wilson STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 24 03:56 EDT 2024. Contains 372771 sequences. (Running on oeis4.)