# Problem 187: Semiprimes
A composite is a number containing at least two prime factors. For
example, 15 = 3 × 5; 9 = 3 × 3; 12 = 2 × 2 × 3. There are ten composites
below thirty containing precisely two, not necessarily distinct, prime
factors: 4, 6, 9, 10, 14, 15, 21, 22, 25, 26. How many composite
integers, n < 108, have precisely two, not necessarily distinct,
prime factors?