021.py

#!/usr/bin/env python

# Let d(n) be defined as the sum of proper divisors of n (numbers less
# than n which divide evenly into n). If d(a) = b and d(b) = a, where
# a b, then a and b are an amicable pair and each of a and b are
# called amicable numbers. For example, the proper divisors of 220 are
# 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) =
# 284. The proper divisors of 284 are 1, 2, 4, 71 and 142; so d(284) =
# 220. Evaluate the sum of all the amicable numbers under 10000.

import euler

d = {}
for i in range(10000):
    d[i] = sum(euler.proper_divisors(i))
    
amicable = []
for k,v in d.items():
    if k==v or v>10000:
        continue
    if k == d[v]:
        amicable.extend([k, d[v]])

amicable = list(set(amicable))
print amicable, 'Sum:', sum(amicable)