\documentclass{standalone}
\RequirePackage{tikz}
\RequirePackage{ifthen}
\usetikzlibrary{arrows,shapes}
\tikzstyle{btreeptr} = [draw, ultra thin, fill=blue!50, minimum height=1cm, inner sep=0cm, minimum width=0cm]
\tikzstyle{btreeval} = [draw, semithick, fill=yellow!30, minimum size=1cm]
\tikzstyle{btlink} = [draw, thick, ->, >=triangle 45]
\newcommand{\xyshift}[3]{
  \begin{scope}[xshift=#1, yshift=#2]
    #3
  \end{scope}
}
\newcommand{\btreelink}[2]{
\draw[btlink] (#1.south) -- ([yshift=-0.1cm] #2.north); \&
\fill (#1.south) circle[radius=0.15cm]; \\
}
\newcommand{\btreenodea}[2]{
\matrix [ampersand replacement=\&] (#1)
{
 \node[btreeptr] (#1-a) {\vphantom{1}}; \& \node[btreeval] {#2}; \&
 \node[btreeptr] (#1-b) {\vphantom{1}}; \\
};
}
\newcommand{\btreenodeb}[3]{
\matrix [ampersand replacement=\&] (#1)
{
 \node[btreeptr] (#1-a) {\vphantom{1}}; \& \node[btreeval] {#2}; \&
 \node[btreeptr] (#1-b) {\vphantom{1}}; \& \node[btreeval] {#3}; \&
 \node[btreeptr] (#1-c) {\vphantom{1}}; \\
};
}
\newcommand{\btreenodec}[4]{
\matrix [ampersand replacement=\&] (#1)
{
 \node[btreeptr] (#1-a) {\vphantom{1}}; \& \node[btreeval] {#2}; \&
 \node[btreeptr] (#1-b) {\vphantom{1}}; \& \node[btreeval] {#3}; \&
 \node[btreeptr] (#1-c) {\vphantom{1}}; \& \node[btreeval] {#4}; \&
 \node[btreeptr] (#1-d) {\vphantom{1}}; \\
};
}
\newcommand{\btreenoded}[5]{
\matrix [ampersand replacement=\&] (#1)
{
 \node[btreeptr] (#1-a) {\vphantom{1}}; \& \node[btreeval] {#2}; \&
 \node[btreeptr] (#1-b) {\vphantom{1}}; \& \node[btreeval] {#3}; \&
 \node[btreeptr] (#1-c) {\vphantom{1}}; \& \node[btreeval] {#4}; \&
 \node[btreeptr] (#1-d) {\vphantom{1}}; \& \node[btreeval] {#5}; \&
 \node[btreeptr] (#1-e) {\vphantom{1}}; \\
};
}
\newcommand{\btreenodee}[6]{
\matrix [ampersand replacement=\&] (#1)
{
 \node[btreeptr] (#1-a) {\vphantom{1}}; \& \node[btreeval] {#2}; \&
 \node[btreeptr] (#1-b) {\vphantom{1}}; \& \node[btreeval] {#3}; \&
 \node[btreeptr] (#1-c) {\vphantom{1}}; \& \node[btreeval] {#4}; \&
 \node[btreeptr] (#1-d) {\vphantom{1}}; \& \node[btreeval] {#5}; \&
 \node[btreeptr] (#1-e) {\vphantom{1}}; \& \node[btreeval] {#6}; \&
 \node[btreeptr] (#1-f) {\vphantom{1}}; \\
};
}

\begin{document}
\begin{tikzpicture}
\tikzstyle{every node}=[font=\fontsize{15}{0}\selectfont]
\xyshift{27.5mm}{-30mm}{\btreenoded{b}{1}{2}{3}{4}}
\xyshift{82.5mm}{-30mm}{\btreenoded{c}{5}{6}{7}{8}}
\xyshift{137.5mm}{-30mm}{\btreenoded{d}{11}{12}{13}{14}}
\xyshift{192.5mm}{-30mm}{\btreenoded{e}{16}{17}{18}{19}}
\xyshift{247.5mm}{-30mm}{\btreenodee{f}{21}{22}{23}{24}{25}}
\xyshift{137.5mm}{0mm}{\btreenoded{a}{5}{10}{15}{20}}


\btreelink{a-a}{b}
\btreelink{a-b}{c}
\btreelink{a-c}{d}
\btreelink{a-d}{e}
\btreelink{a-e}{f}
\end{tikzpicture}
\end{document}
