Prime number sieve

prime_number_sieve.rb

def prime_number_sieve(n)
  primes = []
  integers_up_to_n = (2..n).to_a
  integers_up_to_n.each do |i|
    next if i.nil?
    primes << i
    not_prime = i + i
    while (not_prime <= n) do
      integers_up_to_n[not_prime - 2] = nil
      not_prime = not_prime + i
    end
  end
  primes
end