An Elementary Introduction to the Wolfram Language by Stephen Wolfram
The Wolfram Language represents a major advance in programming
languages that makes leading-edge computation accessible to everyone. Unique in its approach of building in vast knowledge and automation, the Wolfram Language scales from a single line of easy-to-understand interactive code to million-line production systems.
Starting Out: Elementary Arithmetic: Elementary Introduction to the Wolfram Language
Diophantine Equation--5th Powers -- from Wolfram MathWorld