<<< tex
e^{
 % below is the complex part:
 \sum_i^n i^2 }
>>> native
[ ESuper
    (EIdentifier "e")
    (EGrouped
       [ EUnderover
           True (ESymbol Op "\8721") (EIdentifier "i") (EIdentifier "n")
       , ESuper (EIdentifier "i") (ENumber "2")
       ])
]