Polynomial division by convolution.

Calculate inverse Z-transform -- (Polynomial division) - Up to K terms,

q(z) = b(z)/a(z),
where
b(z)=b(0)+...+b(k)/z^k +...+b(n)/z^n.
a(z)=a(0)+...+a(k)/z^k +...+a(m)/z^m.
q(z)=q(0)+...+q(k)/z^k +...+q(K)/z^K + ......

If coefficients of b(x) and a(x) are all integers, then the entire process may involve integer arithmetric perations only. The round-off errors may therefore be eliminated.

This code is similar to the code by Tamer Abdelazim Mellik's
"Calculate inverse Z-transform by long division."