# Estimating the Second Frequency Moment

 I just uploaded an updated version of an essay, Estimating the Second Frequency Moment. The frequency moment problem was addressed in the seminal paper of Alon, Matias and Szegedy. In my essay, I give a couple of results from that paper and give indications of how the results can be generalized. Suppose you are shown a stream of numbers $$s_1, s_2, \ldots, s_n$$ where each $$s_j \in {1,2, \ldots, m}$$ for $$j = 1, 2, \ldots, n$$. If $$f_i$$ denotes the number of times \(i…