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.
In [1]:
d = [0]*50000
s = 0
for i in range(1,50000):
for j in range(2*i, 50000, i):
d[j] += i
for i in range(1,10000):
j = d[i]
if j >= 49999:
print('FAIL')
elif d[j]==i and j != i:
s += i
print(s)
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