Here is a collection of puzzles (compiled with Alon Benhaim).
You may find these helpful for Algebraic Number Theory or Algebraic Combinatorics.
oral_exam_practice_problems.pdf
oral_exam_transcript.pdf
cassels_frohlich_exercises.pdf
ted_chinburg_exercises.pdf
Documented notes for lectures given at some point in time. Most handwritten notes are lost.
Baby function field arithmetic
Adelic class groups via two quick examples
Examples of spectral sequences (with Man Cheung Tsui)
The Satake isomorphism
Sum of squares
Little tidbits about the symmetric group
Complex analysis crash course
The Hurwitz existence problem
Here are some documented notes for talks I gave at UPenn's Pizza Seminar.
Jacobi polynomials via pictures
Counting genera of integral quadratic forms
Congruent numbers
Bhargava's cube
The 15 and 290 theorems
Kevin Buzzard gave a summer school on automorphic forms which I was fortunate enough to attend. Here are my handwritten notes.