Solution

ID: past-exam-of-the-options-ii-for-mathematics-and-philosophy-course-of-the-university-of-oxford/2013/n2/c/solution

Inside its radius of convergence a power series can be differentiated term by term. Hence
Every mass is therefore recovered uniquely from the function, proving that the generating function determines the entire distribution. No derivatives at the potentially delicate endpoint one are needed.

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