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Re: Summation question


On Feb 19, 2008, at 1:47 AM, Robert Pigeon wrote:

> Good day all,
>
>             I want to make a summation like this:  Sum[f[i],{i, start,
> finish}]. What I want is that the sum be over a specific set like
> {1,3,5,7,11,13}. So the sum would be : f[1]+f[3]+f[5]+f[7]+f[11]+f 
> [13]. The
> set I want to use is the primes. So, how do I use, if possible, Sum  
> over a
> specific set ?

One way is to map the sum indices to the set elements eg:

Sum[f[Prime[i]],{i,start,finish}]

but this may present problems if the sum is over an infinite range.

Regards,

Sseziwa


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