RE: The prime factors of n.

*To*: mathgroup at smc.vnet.net*Subject*: [mg32718] RE: [mg32673] The prime factors of n.*From*: "Florian Jaccard" <jaccardf at eicn.ch>*Date*: Thu, 7 Feb 2002 05:10:02 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hello Robert ! It's not better than your solution, but it works also ! First create the following function : f[{x_, y_}] := Flatten[Table[Transpose[{{x, y}}][[1]], Evaluate[Transpose[{{x, y}}][[2]]]]] Then the following : g[n_]:=Flatten[Map[f,FactorInteger[n]]] g[72] gives the list you want ! Meilleures salutations Florian Jaccard EICN-HES e-mail : jaccardf at eicn.ch -----Message d'origine----- De : Robert G. Wilson v [mailto:rgwv at kspaint.com] Envoyé : mer., 6. février 2002 09:41 À : mathgroup at smc.vnet.net Objet : [mg32673] The prime factors of n. Hello all, I wish to receive a list of prime factors of n not in the form returned by FactorInteger. Instead I want only the primes the number of times they appear. As an example I will use 72. FactorInteger[72] gives { {2,3}, {3,2} }. I wish the list would read { 2, 2, 2, 3, 3 }. Is the following the best that I can do? f[n_Integer] := Module[{a = FactorInteger[n], b = {}}, While[Length[a] > 0, Do[b = Append[b, a[[1, 1]]], {a[[1, 2]]}]; a = Drop[a, 1]]; b] . See http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?An um=037276 Sincerely yours, Robert G. "Bob" Wilson, V