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MathGroup Archive 2005

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Re: defining a recursive formula?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54896] Re: [mg54869] defining a recursive formula?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 5 Mar 2005 01:34:40 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

p[R_] := i*R-a;

f1[n_Integer?Positive] := Nest[p,R,n];

f2[1] = p[R];
f2[n_Integer?Positive] := 
    f2[n] = p[f2[n-1]];

Needs["DiscreteMath`RSolve`"];

f3[n_Integer?Positive]=f3[n] /. 
      RSolve[{
            f3[n]==i*f3[n-1]-a,
            f3[1]==i*R-a},
          f3[n],n][[1]]//FullSimplify

(a - i^n*(a - i*R + R))/(i - 1)

These are all equivalent

And@@(Table[f1[n]==f2[n]==f3[n],{n,20}]//Simplify)

True


Bob Hanlon

> 
> From: "lou zion" <illuzioner at adelphia.net>
To: mathgroup at smc.vnet.net
> Date: 2005/03/04 Fri AM 05:08:04 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg54896] [mg54869] defining a recursive formula?
> 
> can someone help me represent the following?
> 
> i have a quantity p[R_] := i* R -a
> 
> i need to compute
> 
> F[N_]  := p[p[p[p[p[R]]]]]  to N levels deep.
> 
> how can i do this? thanks!
> 
> lou
> 
> 
> 


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