\documentclass{article}
\usepackage[letterpaper,margin=1in]{geometry}
\usepackage{tikz}
\usetikzlibrary{datavisualization}
\begin{document}
\begin{figure}[h]
\centering
\tikz
\datavisualization [
  scientific axes = inner ticks,,
  %% uncomment the next line and comment out the one after that for
  %% equal horizontal and vertical scale
  % all axes={unit length=1in per 33 units},
  x axis = {length = 6 in}, y axis = {length = 4 in},
  visualize as line
]
% https://oeis.org/A000720/b000720.txt first 200 entries
data [separator=\space] {
x y
1 0
2 0
2 1
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};
\caption{Number of primes below $n$, for small $n$}
\end{figure}
\end{document}
