Sierpinski TikZ

\documentclass[multi=tikzpicture]{standalone}
\usepackage{tikz}

\newcommand{\sier}[1]{
  \fill[white,draw=black,line join=bevel] (30:1) -- (150:1) -- (270:1) -- cycle;
  \node[red,transform shape] at (0,0) {#1};
  \ifnum#1>0
    \foreach \theta in {90,210,330}
    {
      \begin{scope}[shift={(\theta:1)},scale=0.5]
        \expandafter\sier\expandafter{\the\numexpr#1-1\relax}
      \end{scope}
    }
  \fi
}

\begin{document}

\begin{tikzpicture}
  \fill[green,draw=black] (90:2) -- (210:2) -- (330:2) -- cycle;
  \sier4
\end{tikzpicture}

\end{document}