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