Re: Listing
- To: mathgroup at smc.vnet.net
- Subject: [mg34131] Re: [mg34114] Listing
- From: BobHanlon at aol.com
- Date: Sun, 5 May 2002 04:48:37 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
In a message dated 5/4/02 6:04:32 AM, ab106 at pixie.co.za writes:
>I am working on a project investigating the Pell equation x^2-d*y^2=1,
>where
>I calculate the values of d keeping y constant and determining the periodic
>behaviour of x and d. I have found using Mathematica most useful to find
>the
>integer values of x and d. However, when I use Table[{(x^2-1)/y^2},{x,n,m}],
>it lists all the rational fractions over the complete range of n to m which
>I choose, where I am interested only in getting the Integer values of x
>and
>d while y is kept constant for one set of calculations.
>I wonder if it is possible for someone to advise me on how I must change
>my
>Table listing to only give the Integer values of x and d. I have tried
>several changes but none worked.
>
For a given (y, m, n) use either
Cases[Table[{x, (x^2-1)/y^2},{x,m,n}],
{_, _Integer}]
or
Select[Table[{x, (x^2-1)/y^2},{x,m,n}],
Head[#[[2]]]==Integer&]
Bob Hanlon
Chantilly, VA USA