Enter an integer n below to see if n is a prime #, the nth
prime, the # of primes <= n (pi(n) & its estimate), or a list of
primes <= n.
The algorithm used is based on the well-known method for finding primes called
Sieve of Eratosthenes. In estimating pi(n), we use the Prime
Number Theorem which states that the ratio of pi(n) to n/ln(n)
-> 1 as n -> infinity.