These are notes on elementary number theory; that is, the part of number theory which does not involves methods from abstract algebra or complex variables.
The first link in each item is to a Web page; the second is to a PDF file. Use the PDF if you want to print it.
[November 21, 2024] I fixed a typo in the notes on the Fermat-Pell equation in the last example. (Two people have pointed this out, and I hope it's fixed now!)
[November 10, 2024] I fixed a typo in the notes on periodic continued fractions.
[December 14, 2022] I updated the Chinese Remainder Theorem notes with a proof of the last theorem (on non-relatively prime moduli).
[August 11, 2022] I clarified the assumptions in many of the results on finite continued fractions (so all the a's are positive reals except that a0 can be nonnegative), and added a part to the last example.
[June 28, 2019] These notes were revised in Spring, 2019. I revised the sections on infinite continued fractions and periodic continued fractions after the term during May and June. I'm planning to add sections on purely periodic continued fractions and continued fractions for radicals, and expand the sections on the Fermat-Pell equation.