Re: Summation question

*To*: mathgroup at smc.vnet.net*Subject*: [mg85706] Re: Summation question*From*: dh <dh at metrohm.ch>*Date*: Tue, 19 Feb 2008 07:07:21 -0500 (EST)*References*: <fpdu7v$qlq$1@smc.vnet.net>

Hi Robert, applying Prime to a range of integers gives the prime indices (note that by definition 1 is not but 2 is prime). Then we map f onto these primes and finally use Total to get the sum: Total[f /@ Prime@Range[6]] hope this helps, Daniel 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 ? > > > > Thanks, > > > > Robert > > > > Robert Pigeon > >