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 Quote by RandomMystery I can't understand the sum notation shown in Wikipedia or in this article: http://mathforum.org/library/drmath/view/53159.html I want to find the sum notation for (a+b+c)^n however I can't understand the sum notation: [snip] I also don't understand, is that they are taking the some from i,k,j to what? Shouldn't their be a number on top of the sigma? I would appreciate the help!
Adding to Micromass's remarks, the summation is meant to be over all triples i, j, k where $i \ge 0, j \ge 0, k \ge 0$ and $i+j+k=n$