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MathGroup Archive 2000

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Re: PrimeQ queries

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24351] Re: [mg24213] PrimeQ queries
  • From: "Greg Keogh" <greg at mira.net>
  • Date: Sun, 9 Jul 2000 04:52:55 -0400 (EDT)
  • References: <8jrcsg$e14@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Harvery,

> The two examples you give of numbers which PrimeQ incorrectly
> reports as prime are themselves in error.  PrimeQ in Version 4.0 correctly
> reports both of them as not being prime.

Have you any idea why Mathematica Student Version 2.2.4 would do this?

Q1 = 89*11551*37159;
Q2 = 7309*321553*2828197;
PrimeQ[Q1]
PrimeQ[Q2]
FactorInteger[Q1]
FactorInteger[Q2]

=True
=True
={{38200901201, 1}}
={{6646915915638769, 1}}

What's so "magical" about these numbers? The notebook where I discovered
these peculiar numbers has this comment near the top:

Developed for MA 408 at Michigan Technological University
by S.W. Graham March 1995

I might try to contact the author to see what he knows.

Ps. After years of delay, I expect to upgrade to Version 4 sometime in the
next week-or-two. Hurrah!

Cheers,
Greg




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