Re: Summations with Primes

*To*: mathgroup at smc.vnet.net*Subject*: [mg40011] Re: [mg39932] Summations with Primes*From*: Helge Andersson <helge at envic.chalmers.se>*Date*: Sun, 16 Mar 2003 02:20:15 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Anthony, here is one simple way which is quit fast. p[i_]:=Prime[i]; imin=3; imax=40000; Plus@@Table[p[i],{i,imin,imax}]//Timing Out[21]= {0.571 Second,9160579434} Then, if you like to have an extra function g that takes p just wrap it over p[i] such as , In[19]:= g[x_]:=N[1/x]; Plus@@Table[g[p[i]],{i,imin,imax}]//Timing Out[20]= {1.062 Second,1.99946} A more comprehensive way to write the code can be done using & and # which is almost as fast as the previous example. In[54]:= Plus@@(g@p@#&/@Range[imin,imax])//Timing Out[54]= {1.072 Second,1.99946} /Helge Chalmers Sweden At 02:29 2003-03-12 -0500, you 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? > >Thank you for your time > >Anthony Felder