Bill Allombert on Fri, 04 Dec 2009 00:27:46 +0100


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Re: Getting more than one value out of a function


On Thu, Dec 03, 2009 at 01:18:35PM -0800, curiousity wrote:
> 
> Hi.
> How do I tell PARI I want to repeatedly evaluate a function to get out more
> than one value?
> 
> I've entered: n=0;n=n+1;r=prod(a=1,n-1,1-1/prime(a))/prime(n) .
> 
> PARI spits out 1/2, but I want 1/2, 1/6, 2/30, 8/210, 48/2310, 480/30030,
> etc.
> 
> I've been poking through the tutorial and online help, but most of it is
> aimed at an audience that is more math-competent and computer-savvy than I.
> If anyone is willing to take the time to post a step-by-step text
> description, it would really help me get going.

Use the vector function:
? vector(10,n,prod(a=1,n-1,1-1/prime(a))/prime(n))
%4 = [1/2, 1/6, 1/15, 4/105, 8/385, 16/1001, 192/17017, 3072/323323, 55296/7436429, 110592/19605131]

or use for:
? for(n=1,20,print(prod(a=1,n-1,1-1/prime(a))/prime(n)))
1/2
1/6
1/15
...

Cheers,
Bill.