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MathGroup Archive 1997

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Multiple sums.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5759] Multiple sums.
  • From: Gadi Oron <oron at tremois.pmmh.espci.fr>
  • Date: Tue, 14 Jan 1997 10:42:32 -0500
  • Organization: Acces regional Ile-de-France (Univ. Paris VI/VII) - France
  • Sender: owner-wri-mathgroup at wolfram.com

Hi there, 

I would like to thank all of those who had replied to my previeous 
questions, that was very helpful.

So now for a new one :

I want to do a multiple sum with a variable number of variables (hehe)
something of this type :

Sum[f1(n[1],..,n[M])*Sum[f2(n[1],..,n[M])* ..., {n[1],1,g1(n[1],...)},...]

so I wrote; (Well, i've copied it directly so the functions f and g are 
already there)

sl[L_,n_]:=Module[{r=1-n/L,t,l},
        t=(L r+1-Sum[l[p],{p,1,n-1}]); 
        For[ii=n-1,ii>0,ii--,
                t=Sum[(1+l[ii])*t,{l[ii],0,L r-Sum[l[k],{k,1,ii-1}]}];
        ];
        Return[t];
]

Well, it is quite unreadeble but whats essential is that the ii in the range
index won't evaluate, so the sums are made with (litterally) l[ii] and
not with l[1],l[2] etc,

I even tried to evaluate the ranges before, putting 
a={l[ii],0,L r-Sum[l[k],{k,1,ii-1}]}
t=Sum[... ,a]

But then MM yells that the range is incorrect.

Any ideas?

P.S. : Excuse me for being unclear about this one.

See ya.
/\/\/\/\/\/\/\/\/\/\/\/>> Gadi ORON <<\/\/\/\/\/\/\/\/\/\/\/\/\
| EMAIL :  oron at pmmh.espci.fr   ::::     oron at clipper.ens.fr  |
| Homepage : http://pmmh.espci.fr/home/oron/WWW/personal.html |
| fido : 2:325/302.8                                          |
| 		  Soyez braves - be brave.                    |
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