Re: recursion on TI-86

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Re: recursion on TI-86
From: RWW Taylor <RWTNTS@RITVAX.ISC.RIT.EDU>
Date: Mon, 21 Dec 1998 10:49:45 -0500
Reply-To: RWW Taylor <RWTNTS@RITVAX.ISC.RIT.EDU>

Ax-Man <krw699@AOL.COM> writes:

> Can anybody tell me how to evaluate a recursively defined sequence.
>
> a(1) = 2
> a(n) = a(n-1) + (4/a(n-1))
>
> I have a ti 86 and cannot find out how to do this.  my friends are able to
> do it on their 82's and 85's but I cant.

Daniel Moraseski suggests

   2<ENTER>Ans+4/Ans<ENTER><ENTER><ENTER>...

but is told

> No, I need to evaluate and graph this recursive sequence as well as get its
> values at from n=1000 to n=1009.

The suggestion made was just the simplest, home-screen way to generate the
successive terms. If you want to _store_ the successive values as well as see
them, first create a list names, say, aa to hold these values (is it the
NEWLIST command also on the TI-86?). Then use:

2-->aa[1] : 1-->n    <ENTER>
n+1-->n : aa[n-1] + 4/aa[n-1]-->aa[n]   <ENTER>
<ENTER> <ENTER> ....

If you don't want to press the ENTER key so many times, write a tiny program
involving a For or While loop.

But you really shouldn't have to generate more than a few terms before you can
_predict_ what the terms past n=1000 will be!   :-)}

------------------------------------------------
RWW Taylor
National Technical Institute for the Deaf
Rochester Institute of Technology
Rochester NY 14623

>>>> The plural of mongoose begins with p. <<<<