Python, arguable most readable: divisors = lambda n: (k for k in range(1, n / 2 + 1) if n % k == 0) perfects = (n for n in itertools.count(1) if n == s

Python, arguable most readable: divisors = lambda n: (k for k in range(1, n / 2 + 1) if n % k == 0) perfects = (n for n in itertools.count(1) if n == sum(divisors(n)))