I've been testing my recursive function against your iterative function, and yours is generally a quite steady 50% faster on factorizing 2**n +/- 1 for 0 < n < 60. I think that, for a challenge, I'll try to make a recursive function that matche or beats the iterative function -- it's worth the experiment!
Cheers, MTD -- http://mail.python.org/mailman/listinfo/python-list
