what is the problem with this code ?!!

n=1:20;
syms n z
a = ztrans(3*(-1/4)^n);
subplot(2,1,1)
stem(a)

Answer 1

[Azzi Abdelmalek]

syms n z
a = ztrans(3*(-1/4)^n);
b=subs(a,1:20)
subplot(2,1,1)
stem(b)