boost_1_45_0/libs/math/doc/sf_and_dist/equations/expint_n_5.mml

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <msub>
      <mi>E</mi>
      <mn>1</mn>
    </msub>
    <mfenced>
      <mrow>
        <mi>x</mi>
      </mrow>
    </mfenced>
    <mo>=</mo>
    <mfrac>
      <msup>
        <mi>e</mi>
        <mrow>
          <mo>&#x2212;</mo>
          <mi>x</mi>
        </mrow>
      </msup>
      <mi>x</mi>
    </mfrac>
    <mfenced>
      <mrow>
        <mn>1</mn>
        <mo>+</mo>
        <mi>R</mi>
        <mfenced>
          <mrow>
            <mfrac>
              <mn>1</mn>
              <mi>x</mi>
            </mfrac>
          </mrow>
        </mfenced>
      </mrow>
    </mfenced>
  </mrow>
</math>