Problem 021

git-svn-id: file:///srv/svn/euler@48 e5f4c3ec-3c0c-11df-b522-21efaa4426b5

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))