title: Program is returning 0
body: <p>I am currently tackling problem 23 on Project Euler and my code keeps returning nothing when I am trying to compare a set of numbers from 1 - 28123 and a list of numbers that contain all the possible combinations of 2 abundant numbers below 28123. So that I can remove them later, apologies for the inefficient code, any comments of efficiency would be very appreciated.</p>
  
  <p>All I know is that I'm relatively confident the code 'lisp' and before should be correct. Cheers!</p>
  
  <pre><code>import itertools
  
  success = []
  flatten_iter = itertools.chain.from_iterable
  
  
  def factors(n):
      return set(flatten_iter((i, n//i)
                              for i in range(1, int(n**0.5)+1) if n % i == 0))
  
  for x in range(1, 28124):
      if (sum(list(factors(x))) - x) &gt; x:
          success.append(x)
  
  lisp = []
  for x in success:
      lisp.append(2 * x)
  
  numbers = []
  for x in range(1, 28124):
      numbers.append(x)
  
  prefinal = [x + y for x in success for y in success]
  zipped = zip(prefinal, lisp)
  final = set(zipped).intersection(numbers)
  
  print(final)
  </code></pre>