Unfortunately, I can't solve the problem in MAPLE that appears in the last line of the picture (0=1 instead of a₀=1) unless I write a₀ seperately and add the partial sum starting from k=1 to it.

I assume the problem is with 0⁰ in the power series but since MAPLE defines 0⁰:=1 I'm not sure about it. Anyone knows a better solution or can tell me if I made a mistake somewhere?