アルティン・ハッセの指数関数
David Roberts provided a natural combinatorial link between the Artin–Hasse exponential and the regular exponential in the spirit of the ergodic perspective (linking the "p"-adic and regular norms over the rationals) by showing that the Artin–Hasse exponential is also the generating function for the probability that an element of the symmetric group is unipotent in characteristic "p", whereas the regular exponential is the probability that an element of the same group is unipotent in characteristic zero.