Solve 73 in Python.

python/e073.py

@@ -1,8 +1,35 @@
 
+def get_farey_series_length_recursive(d_1, d_2, d_max):
+    if d_1 + d_2 > d_max:
+        return 0
+    d_med = d_1 + d_2
+    l_min = get_farey_series_length_recursive(d_1, d_med, d_max)
+    l_max = get_farey_series_length_recursive(d_med, d_2, d_max)
+    return l_min + 1 + l_max
+
+
+def get_farey_series_length(d_1, d_2, d_max):
+    new_pairs = [(d_1, d_2)]
+    s = 0
+
+    while new_pairs:
+        pairs = new_pairs
+        new_pairs = []
+        for d_1, d_2 in pairs:
+            d_new = d_1 + d_2
+            if d_new <= d_max:
+                s += 1
+                new_pairs.append((d_1, d_new))
+                new_pairs.append((d_new, d_2))
+    return s
+
+
 def euler_073():
-    return 0
+    d_max = 12000
+    s = get_farey_series_length(2, 3, d_max)
+    return s
 
 
 if __name__ == "__main__":
     print("e073.py: " + str(euler_073()))
-    assert(euler_073() == 0)
+    assert(euler_073() == 7295372)