Implementing an amicable number algorithm

In this section, we are going to find a solution in Ruby for the math problem that asks this: evaluate the sum of all the amicable numbers under 10,000.

So that made perfect sense, right? In case your amicable number knowledge is a little rusty like mine was, let's look at a definition of amicable numbers:

Let d(n) be defined as the sum of proper divisors of n (numbers less than n that could be divided evenly into n). If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair, and both a and b are called amicable numbers.

Still unclear? The following is the full explanation:

Essentially, you take a number, identify all its divisors, and add them together to get a value. Next, take that final sum value, identify its divisors, and add them together. If this second sum value is the same as the original number for which you found divisors in the first place, then both the original number and its final sum are considered amicable numbers.

The...