[seqfan] Re: A new sequence

Robert Munafo mrob27 at gmail.com
Tue Feb 5 21:06:35 CET 2013


Sorry Max, it looks like I was writing my reply while you wrote yours (-:

Anyway, you answered my question (the PARI/GP code is great [1],
thanks), and also explained why Guy had his polynomials "backwards"
(with the highest power of the variable first).

Recurrence relations (or iterative formulas, or recursive definitions,
as I call them), very straightforward.

So I guess we just need to know which of the 1000 or so are recurrence
relations, and of those which sets of initial terms and of
coefficients would fit into Richard Guy's request.

I suspect the more interesting ones Guy wants are divisibility
sequences but do not have a recurrence relation (or is that even
possible?)

- Robert

[1] In Pari:
   {linrec(c,a,n=10)=for(k=1,n,a=concat(a,-vecextract(a,Str(-#c,".."))*c~));a}
   linrec([1,-40,206,-40],[-1,0,1,20])

On 2/5/13, Maximilian Hasler <maximilian.hasler at gmail.com> wrote:
>>[...]
> Here, a script which appends n values to
> the r initial values  of a lin.rec. of order r,
> already helps:
>
> (PARI)
> {linrec(c,a,n=10)=for(k=1,n,a=concat(a,-vecextract(a,Str(-#c,".."))*c~));a}
>
> linrec([1,-40,206,-40],[1,0,1,48])
>
> [...]

-- 
  Robert Munafo  --  mrob.com
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-- 
  Robert Munafo  --  mrob.com
  Follow me at: gplus.to/mrob - fb.com/mrob27 - twitter.com/mrob_27 -
mrob27.wordpress.com - youtube.com/user/mrob143 - rilybot.blogspot.com


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