What is a good reference for the story of congruences such as
$$\displaystyle \tau(n) \equiv \sigma(11)(n) \mod\ 691$$
with a conceptual explanation with connections to étale cohomology, etc?
What is a good reference for the story of congruences such as
$$\displaystyle \tau(n) \equiv \sigma(11)(n) \mod\ 691$$
with a conceptual explanation with connections to étale cohomology, etc?
The paper of Swinnerton-Dyer in Lecture Notes in Math 350, as well as Serre's Bourbaki talk on the same topic.
The paper of Deligne, Formes modulaires et représentations $l$-adiques, available at numdam, has these things.