Let M and N be positive integers for which the modular curve X₁ (M, MN) has genus 0, and let p be a prime divisor of MN. This article gives asymptotic lower bounds for the average size of the p-Selmer group of elliptic curves over a number field, with torsion subgroup Z/MZ Z/MNZ. In many cases, it is shown that this average is unbounded.
Tristan Phillips (Thu,) studied this question.