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A047824
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Becomes prime after exactly 5 iterations of f(x) = sum of prime factors of x.
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0
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134, 177, 262, 268, 398, 422, 466, 524, 531, 536, 573, 614, 669, 706, 742, 753, 796, 817, 818, 844, 849, 898, 915, 921, 932, 933, 934, 974, 1006, 1048, 1072, 1149, 1165, 1202, 1222, 1227, 1228, 1238, 1239, 1243, 1294, 1322, 1347, 1354, 1385, 1393, 1398
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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 without multiplicity, so that f(1500) = 2+3+5 = 10.
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LINKS
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MATHEMATICA
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p5iQ[n_]:=PrimeQ[NestList[Total[Transpose[FactorInteger[#]][[1]]]&, n, 5]] == {False, False, False, False, False, True}; Select[Range[2000], p5iQ] (* Harvey P. Dale, May 21 2015 *)
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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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