Re: How to compute this sum?

*To*: mathgroup at smc.vnet.net*Subject*: [mg63066] Re: [mg63041] How to compute this sum?*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Tue, 13 Dec 2005 03:40:48 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

expr=(-6*2^n*n+3*2^n+2*3^n*n)/(3^n)/(n^2-3*n+2)/(2^n); expr//FullSimplify (2*(-3*2^n + 3^n)*n + 3*2^n)/(6^n*((n - 2)*(n - 1))) The term is undefined for n equal to either 1 or 2. Excluding those terms, Sum[Evaluate[expr],{n,3,Infinity}] 1/6 Bob Hanlon > > From: "mizhael" <loseminds at hotmail.com> To: mathgroup at smc.vnet.net > Date: 2005/12/11 Sun PM 10:25:16 EST > Subject: [mg63066] [mg63041] How to compute this sum? > > sum((-6*2^n*n+3*2^n+2*3^n*n)/(3^n)/(n^2-3*n+2)/(2^n),n = 1 .. Inf) > > thanks a lot! > > >