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<head><title>polygamma2</title>
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<body>
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
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      <mi>&#x03C8;</mi>
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        <mo>&#x2212;</mo>
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    <mo>=</mo>
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          <mo>&#x2212;</mo>
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      <mi>&#x03C8;</mi>
      <mrow>
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          <mrow>
            <mi>n</mi>
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    <mfenced>
      <mrow>
        <mi>x</mi>
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    <mo>+</mo>
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          <mo>&#x2212;</mo>
          <mn>1</mn>
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    <mi>&#x03C0;</mi>
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          <mo>&#x2202;</mo>
          <mi>n</mi>
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        <mi>cot</mi>
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        <mo>&#x2202;</mo>
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          <mi>x</mi>
          <mi>n</mi>
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