for x1,x2=0,1,2,… such that x1+x2>0. The simulation proceeds in two steps: First, X1
is simulated from the modified logarithmic distribution with parameters p~1=p1/(1−p2) and δ1=log(1−p2)/log(1−p). Then we simulate X2 conditional on X1. We note that X2∣X1=x1 follows the logarithmic series distribution with parameter p2 when x1=0, and the negative binomial distribution with parameters (x1,p2) when x1>0.