multiplicity function edited , now returns inifinity when n equals 0, and also returns infinty when p equals 2 and n equals zero, which previously was returning zero 

for issues #8159 and #8145
But the docstring says "if n == 0 return oo" but this isn't the whole story. You do so only if p >=2. So what is the motivation to do so. Do you have a reference for this result?