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Re: Splitting sums in mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg126854] Re: Splitting sums in mathematica
• From: "james.a.gordon1" <james.a.gordon1 at googlemail.com>
• Date: Wed, 13 Jun 2012 04:57:39 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <jqusrg$rnm$1@smc.vnet.net>

Hi Koopman,

Thanks for the quick reply, I believe your suggestions solve some of my problem. To further clarify my question, I have an equation that looks like this

F = (X - Y1 - Y2 - Y3 + Z)^2

X = Sum_p Sum_q Sum_r [a_p*a_q*a_r]

Yi = Sum_p Sum_q!=p b_p*b_q, where different X_i have different terms in the sums

Z = Sum_p Sum_q!=p Sum_r!=q!=p

In other words I end up with a large number of terms, each of which can have as many as 6 nested sums, all of which need to be expanded resulting in hundreds of terms. I want mathematica to algebraically expand these nested sums for me rather than me having to type up the expanded form myself. I believe with your solution I would still need to manually keep track of the indices for each expansion. 

Once all the nested sums are expanded, I will make some substitutions of the a, a^2, a^3...a^6 terms, then simplify. At no point to I need to calculate this with real values, I just need an algebraic expression.

Thanks again

James