APL will be 50 years old in November 2016 (50 years from 1966-11-27 15.53.58, to be exact), and it remains unsurpassed in manifesting Kenneth E. Iverson's five important characteristics of notation:

- ease of expression
- suggestivity
- subordination of detail
- economy
- amenability to proof

These characteristics are demonstrated by working through 16 APL expressions. The material is approachable for beginners and yet thought-provoking for experts.

One of the 16 expressions is a fast computation of the partition function without use of the Hardy-Ramanujan (1918) results.