ABSTRACT
All mathematics begins with counting. This is the process of putting the set of objects to be counted in one-to-one correspondence with the first several natural numbers (or counting numbers):
1, 2, 3, 4, 5, · · · . We denote by N the infinite set consisting of all these numbers. Amazingly, despite the
antiquity of its study, humankind has barely begun to understand the algebra of this set. This introduction is intended to provide you with a fund of examples and principles that we will generalize in later chapters.
