<<< omml
<?xml version="1.0" encoding="UTF-8"?>
<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:supHide m:val="on" />
        <m:supHide m:val="on" />
      </m:naryPr>
      <m:e>
        <m:r>
          <m:rPr>
            <m:sty m:val="p" />
          </m:rPr>
          <m:t>P</m:t>
        </m:r>
      </m:e>
      <m:sub />
      <m:sup>
        <m:m>
          <m:mPr>
            <m:baseJc m:val="center" />
            <m:plcHide m:val="on" />
            <m:mcs>
              <m:mc>
                <m:mcPr>
                  <m:mcJc m:val="center" />
                </m:mcPr>
              </m:mc>
              <m:mc>
                <m:mcPr>
                  <m:mcJc m:val="left" />
                </m:mcPr>
              </m:mc>
            </m:mcs>
          </m:mPr>
          <m:mr>
            <m:e>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>0</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>&lt;</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>i</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>&lt;</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>m</m:t>
              </m:r>
            </m:e>
          </m:mr>
          <m:mr>
            <m:e>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>0</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>&lt;</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>j</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>&lt;</m:t>
              </m:r>
              <m:r>
                <m:rPr>
                  <m:sty m:val="p" />
                </m:rPr>
                <m:t>n</m:t>
              </m:r>
            </m:e>
          </m:mr>
        </m:m>
      </m:sup>
    </m:nary>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>(</m:t>
    </m:r>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>i</m:t>
    </m:r>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>,</m:t>
    </m:r>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>j</m:t>
    </m:r>
    <m:r>
      <m:rPr>
        <m:sty m:val="p" />
      </m:rPr>
      <m:t>)</m:t>
    </m:r>
  </m:oMath>
</m:oMathPara>

>>> native
[ EUnderover
    True
    (ESymbol Op "\8721")
    (EGrouped [])
    (EArray
       [ AlignCenter ]
       [ [ [ ENumber "0"
           , ESymbol Rel "<"
           , EIdentifier "i"
           , ESymbol Rel "<"
           , EIdentifier "m"
           ]
         ]
       , [ [ ENumber "0"
           , ESymbol Rel "<"
           , EIdentifier "j"
           , ESymbol Rel "<"
           , EIdentifier "n"
           ]
         ]
       ])
, EIdentifier "P"
, ESymbol Open "("
, EIdentifier "i"
, ESymbol Pun ","
, EIdentifier "j"
, ESymbol Close ")"
]