println["The first 20 primes are: " + first[primes[], 20]]
println["The primes between 100 and 150 are: " + primes[100,150]]
println["The number of primes between 7700 and 8000 are: " + length[primes[7700,8000]]]
println["The 10,000th prime is: " + nth[primes[], 10000-1]]  // nth is zero-based