Added Carmichael Numbers and found error in mr function in sympy.
Added Carmichael Numbers and found error in mr function in sympy.

These are special set of numbers which contradicts Fermat primality test and hence Miller Rabin and various other probabilistic prime tests given in sympy/ntheory/primetest.py
as can be seen here : https://en.wikipedia.org/wiki/Carmichael_number
kaushik94/sympy,kaushik94/sympy,kaushik94/sympy