Friday Oct 20

Finished proving unique factorization.
Noted that in other contexts, like Z[i] and Z[sqrt{-5}], the primes may be different, and unique factorization may fail.
Used unique factorization to study the following question: what fraction of integer points in the plane are visible from the origin? Answer: 6/pi².
Notation: p^a || n if p is prime and p^a|n but p^a+1 doesn't |n.