Random: unsigned int gsl_ran_geometric(const gsl_rng * r, double p)
This function returns a random integer from the geometric distribution,
the number of independent trials with probability p until the
first success. The probability distribution for geometric variates
is,
for @c{$k \ge 1$}
@math{k >= 1}.
Function: double gsl_ran_geometric_pdf(unsigned int k, double p)
This function computes the probability @math{p(k)} of obtaining k
from a geometric distribution with probability parameter p, using
the formula given above.