\documentclass[border={10pt}]{standalone}
\usepackage{tikz,pgfplots,filecontents,amsmath}
\pgfplotsset{compat=1.5}

\begin{filecontents}{data.dat}
 n   yn 
0    1
1    2
2    4
3    6
4    8
5    10
6    12
7    14
8    16
9    0
10   0
\end{filecontents}


\begin{document}
\begin{tikzpicture}
\begin{axis}
[%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    axis x line=middle,
    axis y line=middle,
    every axis x label={at={(current axis.right of origin)},anchor=north west},
    every axis y label={at={(current axis.above origin)},anchor= north west},
    every axis plot post/.style={mark options={fill=black}},
    xlabel={$n$},
    ylabel={$\boldsymbol{y[n]}$},
    xtick={0,1, ..., 11},
    xmax=11,
    yticklabels={
    	$a^0$,
    	$a^1$,
    	$a^2$,
    	$a^3$,
    	$a^4$,
    	$a^5$,
    	$a^6$,
    	$a^7$,
    	$a^8$,
    	$a^9$,
    	$a^10$
    },
    ymin=0,
    ymax=20,
]%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\addplot+[ycomb,black,thick] table [x={n}, y={yn}] {data.dat};
\end{axis}
\end{tikzpicture}

\end{document}