daviddavis

def prime_factorization(num)

  prime =  Enumerator.new do |y|
    mem = []
    is_prime = lambda { |e| mem.find { |_| e.gcd(_) != 1 } }
    2.upto(num) do |n|
      unless is_prime[n]
        mem << n
        y << n
      end