sympy/sympy — pull request #670 by smichr (2011-10-19 19:09:41+00:00)
Title: allow 4**x -> 2**(2*x) again

The reason for allowing this behavior is that (2**4)**x automatically
becomes 16**x and you can no longer 'see' the exponent of 4. In order
to allow terms to become canonical wrt bases, this function allows
that "hidden" 4 to be recovered so 2**(4*x) is obtained.