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Re: help working with functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60001] Re: [mg59987] help working with functions
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sun, 28 Aug 2005 03:07:37 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Clear[a]; Clear[seq];
seq = Array[a, 10, 0];

a[0] = 0;
a[1] = 1;
a[k_] := a[k] = a[k - 1] + a[k - 2]

seq
{0, 1, 1, 2, 3, 5, 8, 13, 21, 34}

a[115]
483162952612010163284885

I don't see what the  0 4^(k - 2) term is contributing because it is always
zero - so I left it out. Perhaps you intended something else?

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/


From: hawkmoon269 [mailto:rson at new.rr.com]
To: mathgroup at smc.vnet.net


I have the following program written:

Clear[a]; Clear[seq];
seq = Array[a,10,0]; a[0]=0; a[1]=1;
Do[a[k] = a[k-1] + a[k-2] + 0 4^(k-2), {k,2,10}];
seq

It works fine and correctly outputs

{0, 1, 1, 2, 3, 5, 8, 13, 21, 34}

My sense,though, is that this is inelegant newbie code and am
interested in hearing alternative ways to program with the same output.
 Also, I would like to generalize this as a callable function with
arguments i,j,n...something like:

f[i_,j_,n_]:=
Clear[a]; Clear[seq];
seq = Array[a,n,0]; a[0]=0; a[1]=1
Do[a[k] = a[k-1] + a[k-2] + i j^(k-2), {k,2,n}]
seq

So that

f[0,4,10]

would output

{0, 1, 1, 2, 3, 5, 8, 13, 21, 34}

I've tried variants of the foregoing, but can't get it to work
correctly...

Many thanks in advance for ideas and assistance etc.

h



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