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Math
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This is a test. Here is an equation:
:math:`X_{0:5} = (X_0, X_1, X_2, X_3, X_4)`.
Here is another:

.. math::
    :label: This is a label

    \nabla^2 f =
    \frac{1}{r^2} \frac{\partial}{\partial r}
    \left( r^2 \frac{\partial f}{\partial r} \right) +
    \frac{1}{r^2 \sin \theta} \frac{\partial f}{\partial \theta}
    \left( \sin \theta \, \frac{\partial f}{\partial \theta} \right) +
    \frac{1}{r^2 \sin^2\theta} \frac{\partial^2 f}{\partial \phi^2}

You can add a link to equations like the one above :eq:`This is a label` by using ``:eq:``.