Extract the coefficients of an exponential generating function as
a list of Integers. Since EGF is an instance of Species, the
idea is that labelled can be applied directly to an expression
of the Species DSL. In particular, labelled s !! n is the
number of labelled sstructures on an underlying set of size n
(note that labelled s is guaranteed to be an infinite list).
For example:
> take 10 $ labelled octopi
[0,1,3,14,90,744,7560,91440,1285200,20603520]
gives the number of labelled octopi on 0, 1, 2, 3, ... 9 elements.
