Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?

James Cloos on Thu, 28 Aug 2025 20:37:56 +0200

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Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?

To: pari-users@pari.math.u-bordeaux.fr
Subject: Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
From: James Cloos <cloos@jhcloos.com>
Date: Thu, 28 Aug 2025 14:37:46 -0400
Copyright: Copyright 2025 James Cloos
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BA> Adding this one would break backward compatibility, so this is not
BA> an option.

does pari have a generalized factorial function?

maxima's doc notes this:

     For an argument ‘n’ which is not an integer, float, or rational,
     ‘n!!’ yields a noun form ‘genfact (n, n/2, 2)’.

perhaps pari's docs could suggest using such a generalized factorial
when a double factorial is desired?

-JimC
-- 
James Cloos <cloos@jhcloos.com>
            OpenPGP: https://jhcloos.com/0x997A9F17ED7DAEA6.asc

Follow-Ups:
- Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: Vincent Delecroix <vincent.delecroix@u-bordeaux.fr>

References:
- PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: hermann@stamm-wilbrandt.de
- Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: "Ruud H.G. van Tol" <rvtol@isolution.nl>
- Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: Vincent Delecroix <vincent.delecroix@u-bordeaux.fr>
- Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: hermann@stamm-wilbrandt.de
- Re: PARI/GP wrong on 7!!+7+1 being not prime, or oeis.org/Mathematica?
  - From: Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>

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