count_primes

Problem

Count the number of prime numbers less than a non-negative number, n

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References: How Many Primes Are There?

Sieve of Eratosthenes

Solution

Sieve of atkin

[Lehmer method] (http://en.wikipedia.org/wiki/Prime-counting_function)

[Lehmer method implementation] (http://www.codeitive.com/0QNejUPgXU/feasible-implementation-of-a-prime-counting-function-closed.html)