the sequence 2, 3, 5, 7, 11 are the first
five prime numbers.
A prime number is a positive integer which has exactly
2 positive integer factore, one factor being 1 and the
other factor is the positive number itself.
So the next prime numbers after 11 are 13, then 17, 19,
23, 29, 31, 37, 41, 43,...
