1. (Schumer 1.2 # 24) Show that n^3/3 + n^2/2 + n/6 is an integer for n > 0
2. (Schumer 1.3 # 6)
3. Prove that if p is a prime number p > 3, then p^2-1 is divisible by 24.
4. (Schumer 1.4 #7) Prove that no matter which 1001 distinct integers are chosen from { 1, 2, 3, ..., 1991 }, two must have difference 9.
5. Prove by induction that for every n, the binomial coefficient
| / | 2n-1 | \ |
| \ | k | / |