for , where contains only those prime factors . Then the number of for which (i.e., for which all the factors of are is called the deficiency of (Erdős et al. 1993, Guy 1994). The following
table gives the good binomial coefficients
(i.e., those with )
having deficiency
(Erdős et al. 1993), and Erdős et al. (1993) conjecture that
there are no other with .
Erdős, P.; Lacampagne, C. B.; and Selfridge, J. L. "Estimates of the Least Prime Factor of a Binomial Coefficient." Math.
Comput.61, 215-224, 1993.Guy, R. K. Unsolved
Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 84-85,
1994.