\documentclass{minimal}

\usepackage[papersize={4.8cm, 2.6cm}, margin=0cm]{geometry}
\usepackage{tikz}
\pagestyle{empty}

\begin{document}
\raggedright
\begin{tikzpicture}[semithick]
	\clip (-0.4, -0.3) rectangle (4.4, 2.3);

	\foreach \vert in {1, 2, 3} {
		\foreach \horz/\hnum in {1/1, 2/2, 3/3, 4/1, 5/2} {
			\node (a\vert-\horz) at (\horz - 1, 3 - \vert) {$a_{\vert\hnum}$};
		}
	}

	\draw
		(a1-1) -- (a2-2)  (a2-2) -- (a3-3)
		(a1-2) -- (a2-3)  (a2-3) -- (a3-4)
		(a1-3) -- (a2-4)  (a2-4) -- (a3-5);
	\draw [densely dashed]
		(a1-3) -- (a2-2)  (a2-2) -- (a3-1)
		(a1-4) -- (a2-3)  (a2-3) -- (a3-2)
		(a1-5) -- (a2-4)  (a2-4) -- (a3-3);

	\draw [thick, dotted] (2.5, -0.3) -- (2.5, 2.3);
\end{tikzpicture}
\end{document}