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!
>
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>