AlanH
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 Apr 25 accepted Proving a complex equality Apr 25 comment Proving a complex equality So for the trivial case, you can't use the quotient you've set $z$ equal to? Apr 23 comment Proving a complex equality I'm aware of that answer, but I'm looking for an algebraic answer simply because that wouldn't come to me immediately. How did you see that it was an ellipse? I ask because it's not in the familiar form that you see in conic sections of calculus. Apr 23 asked Proving a complex equality Apr 14 asked Number of matrices giving even row and column sum Apr 14 accepted Finding a closed form expression for this sum Apr 13 comment Finding a closed form expression for this sum How do you know that the 2nd term is equal to $(1/\sqrt{1-4x})^2$? Apr 13 comment Finding a closed form expression for this sum @MarcvanLeeuwen How did you search for that? I didn't know how to search for it because there's no specific name or term associated with it. O.w. I'd just have to look through all the results one at a time. Apr 13 asked Finding a closed form expression for this sum Apr 11 accepted Solving functional equation for generating function Apr 11 comment Solving functional equation for generating function But doesn't that change the value of the sum? Apr 11 comment Solving functional equation for generating function Yeah, I've been trying to figure out how to get the indices to start at $0$ all day. Why is it you can just start the the indices (in your hint) at $0$? Apr 11 asked Solving functional equation for generating function Apr 11 comment Simplifying Catalan number recurrence relation @BrianM.Scott In the first half of your answer, how do you go from $1+x\sum_{n\ge 0}\sum_{k=0}^nC_kC_{n-k}x^n$ to $1+x\left(\sum_{n\ge 0}C_nx^n\right)^2$ Apr 10 comment Finding functional equation for generating function yeah, it's not a big deal. :) I was just sort of stating it as an fyi. Apr 10 comment Finding functional equation for generating function your solution doesn't match the solution in the text :[ Apr 10 revised Finding functional equation for generating function added 100 characters in body Apr 10 asked Finding functional equation for generating function Apr 9 comment Functional equations and generating functions oh wow...Thanks for that. Apr 9 accepted Functional equations and generating functions