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 [itex]i \ge 0, j \ge 0, k \ge 0[/itex] and [itex]i+j+k=n[/itex]