def solve():
abundant_numbers = []
for num in xrange(28123 + 1):
#print num
divisors = proper_divisors(num)
if sum(divisors) > num:
abundant_numbers.append(num)
answer = set(xrange(28123 + 1))
for i, x in enumerate(abundant_numbers):
for n in abundant_numbers[i:]:
if n+x > 28123:
break
if n + x in answer:
answer.remove(n+x)
print sum(answer)
def test_proper_divisors_284(self):
self.assertEqual(p021.proper_divisors(284), [1, 2, 4, 71, 142])
def test_proper_divisors_220(self):
self.assertEqual(p021.proper_divisors(220), [1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110])
