  We show that a character sum attached to a family of 3-isogenies defined on
the fibers of a certain elliptic surface over $\mathbb{F}_p$ relates to the
class number of the quadratic imaginary number field $\Q(\sqrt{-p})$. In this
sense, this provides a higher-dimensional analog of some recent class number
formulas associated to 2-isogenies of elliptic curves.
