Re: The prime factors of n.

*To*: mathgroup at smc.vnet.net*Subject*: [mg32727] Re: [mg32673] The prime factors of n.*From*: Chris Johnson <cjohnson at shell.faradic.net>*Date*: Thu, 7 Feb 2002 05:10:24 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

One solution would be... factorIntegerList[n_] := Flatten[PadLeft[{}, #2, #1] & @@@ FactorInteger[n]] (@@@ Is a function of newer versions of Mathematica. It represents Apply at level spec {1}) Chris On Wed, 6 Feb 2002, 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 > >