RE: The prime factors of n.

*To*: mathgroup at smc.vnet.net*Subject*: [mg32717] RE: [mg32673] The prime factors of n.*From*: "Harvey P. Dale" <hpd1 at nyu.edu>*Date*: Thu, 7 Feb 2002 05:10:00 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Bob: This is both more compact and faster: Flatten[Table[#[[1]],{#[[2]]}]&/@FactorInteger[72]] Best, Harvey Harvey P. Dale University Professor of Philanthropy and the Law Director, National Center on Philanthropy and the Law New York University School of Law Room 206A 110 West 3rd Street New York, N.Y. 10012-1074 tel: 212-998-6161 fax: 212-995-3149 -----Original Message----- From: Robert G. Wilson v [mailto:rgwv at kspaint.com] To: mathgroup at smc.vnet.net Subject: [mg32717] [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 ________________________________________________________________________ This email has been scanned for all viruses by the MessageLabs SkyScan service. For more information on a proactive anti-virus service working around the clock, around the globe, visit http://www.messagelabs.com ________________________________________________________________________