From ba3f65ded202907d171727e7d9b2d0c62c9d2f05 Mon Sep 17 00:00:00 2001
From: Robert Altner <robert-altner@t-online.de>
Date: Sat, 23 Feb 2019 02:54:25 +0100
Subject: [PATCH] Added Problem 021

---
 Problem_20.py => Problem_020.py |  0
 Problem_021.py                  | 38 +++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 rename Problem_20.py => Problem_020.py (100%)
 create mode 100644 Problem_021.py

diff --git a/Problem_20.py b/Problem_020.py
similarity index 100%
rename from Problem_20.py
rename to Problem_020.py
diff --git a/Problem_021.py b/Problem_021.py
new file mode 100644
index 0000000..21d361b
--- /dev/null
+++ b/Problem_021.py
@@ -0,0 +1,38 @@
+##########################################################################
+# 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.
+##########################################################################
+
+
+def sumDivisors(x):
+    divisor_sum = 0
+    for j in range(1, int(x / 2) + 2):
+        if (x % j) is 0:
+            divisor_sum += j
+
+    return divisor_sum
+
+
+amicable_number = []
+for i in range(1, 10000):
+    if i in amicable_number:
+        continue
+
+    testing_number = sumDivisors(i)
+    if (i == sumDivisors(testing_number)) and (testing_number != i):
+        amicable_number.append(i)
+
+        if testing_number not in amicable_number:
+            amicable_number.append(testing_number)
+
+sum_of_numbers = sum(amicable_number)
+print(sum_of_numbers)
+
+# Solution: 31626