[seqfan] Re: True (?) reordering
franktaw at netscape.net
franktaw at netscape.net
Fri Mar 5 21:38:14 CET 2010
I would tend to use derangement when referring to the unrestricted
property as a "permutation". If you refer to it as a "reordering",
then "with no fixed points" is probably better.
I prefer "permutation". Note that the index entry for this (which is
missing many sequences in the database) is "permutations, of the
positive (or nonnegative) integers , sequences related to".
Franklin T. Adams-Watters
-----Original Message-----
From: Charles Greathouse <charles.greathouse at case.edu>
Derangement, possibly? It's usually used in a finite context but I
see no reason to avoid it in an infinite one.
Charles Greathouse
Analyst/Programmer
Case Western Reserve University
On Fri, Mar 5, 2010 at 11:40 AM, Maximilian Hasler
<maximilian.hasler at gmail.com> wrote:
> naïvely, I would consider "reordering" as synonym for "bijection",
> and would even accept the identity map as reordering
> (unless additionally given restrictions exclude it, of course).
>
> I don't know if there is a special name for the property you give,
> I often see it explicitely worded as "without a fixed point".
>
> M.
>
> On Fri, Mar 5, 2010 at 5:10 PM, Eric Angelini <Eric.Angelini at kntv.be>
wrote:
>>
>> Hello SeqFans,
>>
>> when one reads in the OEIS something like:
>> "A reordering of the natural numbers", does
>> this mean that we never have n = a(n) in
>> the reordered sequence? If not, is there a
>> name/concept for that?
>>
>> Best,
>> É.
>>
>
>
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