Services & Resources / Wolfram Forums
MathGroup Archive
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

RE: The prime factors of n.

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

	This is both more compact and faster:
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] 
To: mathgroup at
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] .


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

  • Prev by Date: Re: Import variable and data
  • Next by Date: Re: Import variable and data
  • Previous by thread: Re: The prime factors of n.
  • Next by thread: Re: The prime factors of n.