Compute exponential by multiplying previous result

Author: whonore

backoff/_wait_gen.py

@@ -21,12 +21,11 @@ def expo(
     """
     # Advance past initial .send() call
     yield  # type: ignore[misc]
-    n = 0
+    a = 1
     while True:
-        a = factor * base ** n
         if max_value is None or a < max_value:
-            yield a
-            n += 1
+            yield factor * a
+            a *= base
         else:
             yield max_value