Re: The prime factors of n.

*To*: mathgroup at smc.vnet.net*Subject*: [mg32700] Re: [mg32673] The prime factors of n.*From*: Andrzej Kozlowski <andrzej at platon.c.u-tokyo.ac.jp>*Date*: Thu, 7 Feb 2002 05:09:24 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Certainly not. For example f1[n_Integer] := Flatten[Table[#1, {#2}] & @@@ FactorInteger[n]] In[2]:= f1[72] Out[2]= {2,2,2,3,3} is both more elegant and faster. Andrzej Kozlowski Toyama International University JAPAN http://platon.c.u-tokyo.ac.jp/andrzej/ On Wednesday, February 6, 2002, at 05:41 PM, Robert G. Wilson v wrote: > 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?Anum=037276 > > Sincerely yours, > > Robert G. "Bob" Wilson, V > > > >