A sequence of functions is denoted as $\{ f_n \}$ or $(f_n)$. For example,
1. $f:\Bbb R \to \Bbb R$ defined by $f_n(x)=\frac {1}{1+nx^2}$
2. $f:\Bbb R \to \Bbb R$ defined by $f_n(x)=e^{-nx^2}$
3. $f:\Bbb C \to \Bbb C$ defined by $f_n(z)=\frac {\sin nz}{\sqrt n}$