Project Euler 243

problem243.rb

def resiliance limit = Rational(15499,94744)
  list = prime_sieve(23)
  sum = list.map{|x| 1-1.0/x}.reduce(:*)
  val = list.reduce(:*)
  phi = val * sum/(val-1)
  while phi > limit
    list << 2
    val = list.reduce(:*)
    phi = val * sum/(val-1)
  end
  val
end