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\usepackage{tikz}
\usetikzlibrary{trees}
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\begin{document}
%%
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\begin{center}
\begin{tikzpicture}[
  level distance=1.5cm,
  level 1/.style={sibling distance=4cm},
  level 2/.style={sibling distance=2cm},
  level 3/.style={sibling distance=1cm}]
   \node {$f_{n}$}
    child {node {$f_{n-1}$}
          child {node {$f_{n-2}$}
            child {node {$f_{n-3}$}}
            child {node {$f_{n-4}$}}
      }
          child {node {$f_{n-3}$}
            child {node {$f_{n-4}$}}
            child {node {$f_{n-5}$}}
      }
    }
    child {node {$f_{n-2}$}
          child {node {$f_{n-3}$}
            child {node {$f_{n-4}$}}
            child {node {$f_{n-5}$}}
      }
          child {node {$f_{n-4}$}
            child {node {$f_{n-5}$}}
            child {node {$f_{n-6}$}}
      }
    };
\end{tikzpicture}
\[\dots\]
\end{center}
%%
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\end{document}