Re: Special Prime Product

*To*: mathgroup at smc.vnet.net*Subject*: [mg53381] Re: Special Prime Product*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Sat, 8 Jan 2005 23:02:43 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 1/8/05 at 2:39 AM, gilmar.rodriguez at nwfwmd.state.fl.us (Gilmar) wrote: >I'm attempting to form a product: >_____ >| | (p-2) >| | ------- >| | (p-1) >p Prime, p|n >I call the program: ><< NumberTheory`NumberTheoryFunctions` >and use the function "PrimeFactorList" in it, to build >the following module: >specpriprod[n_]:= >Module[{v},v=Product[(primeFactorList[n][[i]]-2)/(primeFactorList[n][[i]]-2), >{i,Length[PrimeFactorList[n]]}];v] >specpriprod is an abbreviation for "Special Prime Product". >When I evaluate: >Table[{n,specprimprod[n]},{n,4,100,2}] >I only get specprimprod[n] = 0 for n even between 4 and 100. But for any even number 2 will be a prime factor. That means p-2 evaluates to zero and the product must be zero. So, there is no apparent problem with the results. I do note your code could be improved and will not do what you describe as written. You are using primeFactorList instead of PrimeFactorList and you have p-2 in the demonimator. Also, you do not need the local variable v. A better approach would be specpriprod[n_]:= Module[{p = PrimeFactorList[n]}, Product[(p[[i]]-2)/(p[[i]]-1),{i,Length[p]}]] And even easier to read and probably more efficient is specpriprod[n_]:= Module[{p = PrimeFactorList[n]}, Times@@((p-2)/(p-1))] -- To reply via email subtract one hundred and four