Re: Re: Summations with Primes
- To: mathgroup at smc.vnet.net
- Subject: [mg40006] Re: [mg39988] Re: Summations with Primes
- From: Kirk Reinholtz <kirk.reinholtz at jpl.nasa.gov>
- Date: Fri, 14 Mar 2003 04:47:39 -0500 (EST)
- References: <200303130806.DAA12131@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Prime/@Range[1,10] will get the first ten primes. Bill Rowe wrote: > > 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.
- References:
- Re: Summations with Primes
- From: Bill Rowe <listuser@earthlink.net>
- Re: Summations with Primes