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RE: Summation without Mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg27449] RE: [mg27416] Summation without Mathematica
• From: "David Park" <djmp at earthlink.net>
• Date: Sun, 25 Feb 2001 20:55:55 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Sum[x^3*a^x, {x, 1, Infinity}]
% /. a -> 7/8
(a + 4*a^2 + a^3)/(-1 + a)^4
18872

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 


> From: mrtommorris [mailto:mor3752 at alltel.net]
To: mathgroup at smc.vnet.net
> 
> Can someone help me to evaluate the sum from x=1 to infinity for the
> expression x^3(7/8)^x. I know the formulas that will evaluate 
> either alone.
> But the product is giving me difficulty.
>