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A075655
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Numbers n such that n + product of prime factors of n = (n+1) + product of prime factors of (n+1).
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0
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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24 + product of prime factors of 24 = 24 + 2 * 3 = 30; 25 + product of prime factors of 25 = 25 + 5 = 30; hence 24 belongs to the sequence.
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MATHEMATICA
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s[n_] := n + Apply[Times, Transpose[FactorInteger[n]][[1]]]; Select[Range[2, 10^5], s[ # ] == s[ # + 1] &]
Flatten[Position[Partition[Table[n+Times@@Transpose[FactorInteger[ n]] [[1]], {n, 2, 100000}], 2, 1], _?(#[[1]]==#[[2]]&), {1}, Heads->False]]+1 (* Harvey P. Dale, Apr 20 2014 *)
rad[n_] := Times @@ First /@ FactorInteger[n]; r1 = 1; s = {}; Do[r2 = rad[n]; If[r1 - r2 == 1, AppendTo[s, n-1]]; r1 = r2, {n, 2, 10^5}]; s (* Amiram Eldar, Aug 23 2019 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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