— Function: unsigned int gsl_ran_pascal (const gsl_rng * r, double p, unsigned int n)

This function returns a random integer from the Pascal distribution. The Pascal distribution is simply a negative binomial distribution with an integer value of n.

          p(k) = {(n + k - 1)! \over k! (n - 1)! } p^n (1-p)^k

for k >= 0

— Function: double gsl_ran_pascal_pdf (unsigned int k, double p, unsigned int n)

This function computes the probability p(k) of obtaining k from a Pascal distribution with parameters p and n, using the formula given above.

— Function: double gsl_cdf_pascal_P (unsigned int k, double p, unsigned int n)
— Function: double gsl_cdf_pascal_Q (unsigned int k, double p, unsigned int n)

These functions compute the cumulative distribution functions P(k), Q(k) for the Pascal distribution with parameters p and n.