Re: Summations with Primes

*To*: mathgroup at smc.vnet.net*Subject*: [mg39988] Re: Summations with Primes*From*: Bill Rowe <listuser at earthlink.net>*Date*: Thu, 13 Mar 2003 03:06:33 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 3/12/03 at 2:29 AM, afelder at crsi.org (Anthony Felder) wrote: >Can you tell me if, when calculating a summation of f(i) where i goes >from imin to imax, Mathematica can be forced to only use prime values >for i? Yes, by adding the appropriate code. That is there isn't a built in directive to do what you want. I think there are two basic approaches. First would be to generate a list of primes, map f to the elements of that list then sum. For example: Tr[f/@Select[Range[imin, imax], PrimeQ]] will do the trick This approach might be made more efficient using the NextPrime function in the package NumberTheory`NumberTheoryFunctions` The other approach would be to modify f so that it returned zero for non-prime arguments. I think this approach is likely to be slower than the first approach.

**Follow-Ups**:**Re: Re: Summations with Primes***From:*Kirk Reinholtz <kirk.reinholtz@jpl.nasa.gov>