Dear Forum
Suppose
that I have a univariate $F(t) = {\sum}_{n \geq 0} a_{n} t^{n}$ or a
bivariate $G(s,t) = {\sum}_{n,k \geq 0} a_{n,k} s^{n}t^{k}$
generating
function on one variable t or two variables s, t respectively,
with all coeffiecients $a_{n}$ or $a_{n,k}$ on the field GF(2) of two
numbers or,
which is actually my case, on the ring GF(2)[X_{1}, X_{2},
..., X_{m}] on $m$ commuting intederminates.
Is there a Gap enviroment
and immediate command or algorithm to compute $a_{n}$ or $a_{n,k}$,
i.e., [t^{n}]F(t) or [s^{n}t^{k}]G(s,t), if we know F or G?
Example: The generating function of Pascal's triangle, taken modulo 2,
is G(s, t) = 1/[1 + (1+t)s]. Suppose I want the binomial coefficient
C(3,8) mod 2,
i.e., the term [s^{3}t^{8}]G(s,t). Can I get it
immediately using a Gap command?
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