factorial1

((m+n)+x)!

W3C sample	WIRIS
	$(n+m+x)!$

<math xmlns="http://www.w3.org/1998/Math/MathML">
  <apply>
    <factorial/>
    <apply>
      <plus/>
      <apply>
        <plus/>
        <ci>n</ci>
        <ci>m</ci>
      </apply>
      <ci>x</ci>
    </apply>
  </apply>
</math>

Author: Design Science, Inc. (E. Cannon, E. Tabacman, R.Miner)