diff --git a/python/e231.py b/python/e231.py
new file mode 100644
index 0000000..5705818
--- /dev/null
+++ b/python/e231.py
@@ -0,0 +1,25 @@
+from lib_prime import prime_factors_count
+from collections import defaultdict
+
+
+def sum_factors(n: int, k: int) -> int:
+    factors_num = defaultdict(int)
+    for i in range(n - k + 1, n + 1):
+        for factor, count in prime_factors_count(i).items():
+            factors_num[factor] += count
+    for i in range(2, k + 1):
+        for factor, count in prime_factors_count(i).items():
+            factors_num[factor] -= count
+    return sum(factor * count for factor, count in factors_num.items())
+
+
+def euler_231():
+    assert sum_factors(10, 3) == 14
+    return sum_factors(20 * 10**6, 15 * 10**6)
+
+
+if __name__ == "__main__":
+    solution = euler_231()
+    print(f"e231.py: {solution}")
+    # assert(solution == 0)
+