What I found most interesting was the sum convergence methods for multiple series.[1] Apparently with simple modifications you can improve the convergence rate

What I found most interesting was the sum convergence methods for multiple series.[1] Apparently with simple modifications you can improve the convergence rate of a multiple series sum by many orders of magnitude, making many multiple sums tractable which weren't before, using relatively simple identities that involve modifying both the summand and the limits of the indices. Off topic: I like to think that combinatorics and statistics have a good-hearted sibling rivalry, both trying to explain what the other cannot but stealing from each others' crib notes all the time. That they meet in the middle with something as expressive as a calculus comes as little surprise. [1] https://fractional-calculus.com/convergence_acceleration_multiple_series.pdf https://fractional-calculus.com/convergence_acceleration_mul...