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Re: Working with indefinite number of variables

• To: mathgroup at smc.vnet.net
• Subject: [mg129151] Re: Working with indefinite number of variables
• From: Cisco Lane <travlorf at yahoo.com>
• Date: Tue, 18 Dec 2012 02:39:04 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
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How about 

sum[x_, n_] := Sum[i*x[[i]], {i, 1, n}]

As long as the x you provide has less than or equal to n parts, it will work.

In[27]:= x = {a, "hello", \[Pi], 17}

Out[27]= {a, "hello", \[Pi], 17}

In[28]:= sum[x, 3]

Out[28]= 2 "hello" + a + 3 \[Pi]