1. Greatest common divisors
3. Linear Diophantine equations
6. The Chinese remainder theorem
9. The number of divisors of an integer
10. The sum of the divisors of an integer
13. Euler's theorem and function
14. Primitive roots and orders
16. Quadratic congruences
18. The quadratic reciprocity theorem
20. Pythagorean triangles
21. x⁴ + y⁴ [not equal] z⁴
23. Sums of three squares
30. Sophie Germain primes
31. The group of multiplicative functions
33. The sum of the reciprocals of the primes
34. The Riemann hypothesis
35. The prime number theorem
37. Factorization and testing for primes
38. Algebraic and transcendental numbers
