Solved 72 in Python.

python/e070.py

@@ -46,6 +46,11 @@ def relative_primes_count_naiv(n):
 
 
 def relative_primes_count_factors(n, fs):
+    """
+    XXX: this method has a bug that first occurs for n = 60. Use totient
+    function from e072.py instead! For some curious reason it is good enough
+    for this problem.  Probably because we only deal with two factors ever.
+    """
     from itertools import combinations
     rel_primes_count = n - 1  # n itself is not a relative prime
     for f in fs: