Python, so they can use [Sage][1].
From their website:

> SageMath is a free <a
 href="http://git.sagemath.org/">open-source</a>   mathematics software
 system licensed under the GPL. It builds on top of many existing 
 open-source packages: <a href="http://numpy.scipy.org/">NumPy</a>, 
<a href="http://www.scipy.org/">SciPy</a>, <a href="http://matplotlib.sourceforge.net/">matplotlib</a>, <a href="http://www.sympy.org/">Sympy</a>,  <a href="http://maxima.sourceforge.net/">Maxima</a>,  <a href="http://www.gap-system.org/">GAP</a>,  <a href="http://www.flintlib.org/">FLINT</a>,  <a href="http://www.r-project.org/">R</a> <a href="./links-components.html">and many more</a>. Access their
 combined power through a common, Python-based language or directly via
 interfaces or wrappers.
  Mission: <em>Creating a viable free
 open source alternative to Magma, Maple, Mathematica and Matlab</em>. 


  [1]: http://www.sagemath.org/