A composite is a number containing at least two prime factors. For example, $15=3\times 5$; $9=3\times 3$; $12=2\times 2\times 3$.

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, $n<{10}^8$, have precisely two, not necessarily distinct, prime factors?