## Equinumerous

Let and be two classes of Positive integers. Let be the number of integers in which are less than or equal to , and let be the number of integers in which are less than or equal to . Then if

and are said to be equinumerous.

The four classes of Primes , , , are equinumerous. Similarly, since and are both of the form , and and are both of the form , and are also equinumerous.