<<< native
[ EUnderover
    True
    (ESymbol Op "\8721")
    (EGrouped [ EIdentifier "m" , ESymbol Rel "=" , ENumber "1" ])
    (ESymbol Ord "\8734")
, EUnderover
    True
    (ESymbol Op "\8721")
    (EGrouped [ EIdentifier "n" , ESymbol Rel "=" , ENumber "1" ])
    (ESymbol Ord "\8734")
, EFraction
    NormalFrac
    (EGrouped
       [ ESuper (EIdentifier "m") (ENumber "2")
       , ESpace (1 % 6)
       , EIdentifier "n"
       ])
    (EGrouped
       [ ESuper (ENumber "3") (EIdentifier "m")
       , EDelimited
           "("
           ")"
           [ Right (EIdentifier "m")
           , Right (ESpace (1 % 6))
           , Right (ESuper (ENumber "3") (EIdentifier "n"))
           , Right (ESymbol Bin "+")
           , Right (EIdentifier "n")
           , Right (ESpace (1 % 6))
           , Right (ESuper (ENumber "3") (EIdentifier "m"))
           ]
       ])
]
>>> omml
<?xml version='1.0' ?>
<m:oMathPara>
  <m:oMathParaPr>
    <m:jc m:val="center" />
  </m:oMathParaPr>
  <m:oMath>
    <m:nary>
      <m:naryPr>
        <m:chr m:val="∑" />
        <m:limLoc m:val="undOvr" />
        <m:subHide m:val="0" />
        <m:supHide m:val="0" />
      </m:naryPr>
      <m:sub>
        <m:r>
          <m:t>m</m:t>
        </m:r>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>=</m:t>
        </m:r>
        <m:r>
          <m:t>1</m:t>
        </m:r>
      </m:sub>
      <m:sup>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>∞</m:t>
        </m:r>
      </m:sup>
      <m:e>
        <m:nary>
          <m:naryPr>
            <m:chr m:val="∑" />
            <m:limLoc m:val="undOvr" />
            <m:subHide m:val="0" />
            <m:supHide m:val="0" />
          </m:naryPr>
          <m:sub>
            <m:r>
              <m:t>n</m:t>
            </m:r>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>=</m:t>
            </m:r>
            <m:r>
              <m:t>1</m:t>
            </m:r>
          </m:sub>
          <m:sup>
            <m:r>
              <m:rPr>
                <m:sty m:val="p" />
              </m:rPr>
              <m:t>∞</m:t>
            </m:r>
          </m:sup>
          <m:e>
            <m:f>
              <m:fPr>
                <m:type m:val="bar" />
              </m:fPr>
              <m:num>
                <m:sSup>
                  <m:e>
                    <m:r>
                      <m:t>m</m:t>
                    </m:r>
                  </m:e>
                  <m:sup>
                    <m:r>
                      <m:t>2</m:t>
                    </m:r>
                  </m:sup>
                </m:sSup>
                <m:r>
                  <m:t> </m:t>
                </m:r>
                <m:r>
                  <m:t>n</m:t>
                </m:r>
              </m:num>
              <m:den>
                <m:sSup>
                  <m:e>
                    <m:r>
                      <m:t>3</m:t>
                    </m:r>
                  </m:e>
                  <m:sup>
                    <m:r>
                      <m:t>m</m:t>
                    </m:r>
                  </m:sup>
                </m:sSup>
                <m:d>
                  <m:dPr>
                    <m:begChr m:val="(" />
                    <m:endChr m:val=")" />
                    <m:sepChr m:val="" />
                    <m:grow />
                  </m:dPr>
                  <m:e>
                    <m:r>
                      <m:t>m</m:t>
                    </m:r>
                    <m:r>
                      <m:t> </m:t>
                    </m:r>
                    <m:sSup>
                      <m:e>
                        <m:r>
                          <m:t>3</m:t>
                        </m:r>
                      </m:e>
                      <m:sup>
                        <m:r>
                          <m:t>n</m:t>
                        </m:r>
                      </m:sup>
                    </m:sSup>
                    <m:r>
                      <m:rPr>
                        <m:sty m:val="p" />
                      </m:rPr>
                      <m:t>+</m:t>
                    </m:r>
                    <m:r>
                      <m:t>n</m:t>
                    </m:r>
                    <m:r>
                      <m:t> </m:t>
                    </m:r>
                    <m:sSup>
                      <m:e>
                        <m:r>
                          <m:t>3</m:t>
                        </m:r>
                      </m:e>
                      <m:sup>
                        <m:r>
                          <m:t>m</m:t>
                        </m:r>
                      </m:sup>
                    </m:sSup>
                  </m:e>
                </m:d>
              </m:den>
            </m:f>
          </m:e>
        </m:nary>
      </m:e>
    </m:nary>
  </m:oMath>
</m:oMathPara>