dskellam                density of the skellam distribution (difference of independent Poissons)
pskellam                cdf of the skellam distribution (difference of independent Poissons)
pskellams               saddlepoint approximation to pskellam
qskellam                quantile(s) of the skellam distribution (difference of independent Poissons)
rskellam                random variates from the skellam distribution (difference of independent Poissons)
