\begin{tikzpicture}
\begin{axis}[
axis lines*=middle,
enlargelimits = true,
ymin=-1,
ymax=1,
xmin=-1,
xmax=20,
axis line style={->,>=stealth},
xlabel={\Large $n$},
ylabel={\Large $x[n]$},
yticklabel style = {yshift=0.2cm},
xticklabel style = {yshift=-0.1cm},
every axis x label/.style={
	at={(ticklabel* cs:1)},
	anchor=north,
},
every axis y label/.style={
	at={(ticklabel* cs:1)},
	anchor=south,
},
ytick={-1, 1},
xtick=\empty,
every outer y axis line/.append style={white!15!black},
every y tick label/.append style={font=\color{white!15!black}},
legend style={draw=white!15!black,fill=white,legend cell align=left}]
\addplot [ycomb, mark=*, fill=white, mark options={scale=1.5, fill=white}, line width=1.5pt, forget plot]
table[row sep=crcr]{
	0 1 \\
	1 0.80902 \\
	2 0.30902 \\
	3 -0.30902 \\
	4 -0.80902 \\
	5 -1 \\
	6 -0.80902 \\
	7 -0.30902 \\
	8 0.30902 \\
	9 0.80902 \\
	10 1 \\
	11 0.80902 \\
	12 0.30902 \\
	13 -0.30902 \\
	14 -0.80902 \\
	15 -1 \\
	16 -0.80902 \\
	17 -0.30902 \\
	18 0.30902 \\
	19 0.80902 \\
	20 1 \\
};

\addplot [black!20, line width=1.5pt, forget plot]
table[row sep=crcr]{
	0 1 \\
	1 0.80902 \\
	2 0.30902 \\
	3 -0.30902 \\
	4 -0.80902 \\
	5 -1 \\
	6 -0.80902 \\
	7 -0.30902 \\
	8 0.30902 \\
	9 0.80902 \\
	10 1 \\
	11 0.80902 \\
	12 0.30902 \\
	13 -0.30902 \\
	14 -0.80902 \\
	15 -1 \\
	16 -0.80902 \\
	17 -0.30902 \\
	18 0.30902 \\
	19 0.80902 \\
	20 1 \\
};

\end{axis}
\end{tikzpicture}