From dfa586dc1f2514ea81cb1d2d13fd9c40279dc71b Mon Sep 17 00:00:00 2001
From: Correl Roush <correl@gmail.com>
Date: Wed, 14 Apr 2010 20:58:26 +0000
Subject: [PATCH] Problem 021

git-svn-id: file:///srv/svn/euler@48 e5f4c3ec-3c0c-11df-b522-21efaa4426b5
---
 e021.py | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 e021.py

diff --git a/e021.py b/e021.py
new file mode 100644
index 0000000..791fe5e
--- /dev/null
+++ b/e021.py
@@ -0,0 +1,28 @@
+from e007 import is_prime
+from e012 import factor
+
+MIN = 2
+MAX = 10000
+
+def proper_divisors(n):
+    """Returns the proper divisors of n
+    
+    Proper divisors are defined as numbers less than n which divide evenly into n
+    """
+    divisors = factor(n)
+    # Knock off the last factor, since it is equal to n
+    return divisors[:-1]
+
+sums = {}
+amicable = []
+i = MIN
+while i < MAX:
+    if not is_prime(i):
+        s = sum(proper_divisors(i))
+        sums[i] = s
+        if s in sums and i == sums[s] and i != s:
+            print i, s, sums[s]
+            amicable.append(i)
+            amicable.append(s)
+    i = i + 1
+print 'Sum of amicable numbers less than {0}: {1}'.format(MAX, sum(amicable))
\ No newline at end of file