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A048131
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Becomes prime or 4 after exactly 9 iterations of f(x) = sum of prime factors of x.
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1
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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
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OFFSET
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1,1
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COMMENTS
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f(x) = sum of prime factors with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22.
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LINKS
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MATHEMATICA
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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 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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