<<< native
[ ESub (EGrouped []) (EIdentifier "p")
, ESub (EIdentifier "F") (EIdentifier "q")
, EDelimited
    "("
    ")"
    [ Right (ESub (EIdentifier "a") (ENumber "1"))
    , Right (ESymbol Pun ",")
    , Right (ESymbol Ord "\8230")
    , Right (ESymbol Pun ",")
    , Right (ESub (EIdentifier "a") (EIdentifier "p"))
    , Right (ESymbol Pun ";")
    , Right (ESub (EIdentifier "c") (ENumber "1"))
    , Right (ESymbol Pun ",")
    , Right (ESymbol Ord "\8230")
    , Right (ESymbol Pun ",")
    , Right (ESub (EIdentifier "c") (EIdentifier "q"))
    , Right (ESymbol Pun ";")
    , Right (EIdentifier "z")
    ]
, ESymbol Rel "="
, EUnderover
    True
    (ESymbol Op "\8721")
    (EGrouped [ EIdentifier "n" , ESymbol Rel "=" , ENumber "0" ])
    (ESymbol Ord "\8734")
, EFraction
    NormalFrac
    (EGrouped
       [ ESub
           (EDelimited
              "(" ")" [ Right (ESub (EIdentifier "a") (ENumber "1")) ])
           (EIdentifier "n")
       , ESymbol Ord "\8943"
       , ESub
           (EDelimited
              "(" ")" [ Right (ESub (EIdentifier "a") (EIdentifier "p")) ])
           (EIdentifier "n")
       ])
    (EGrouped
       [ ESub
           (EDelimited
              "(" ")" [ Right (ESub (EIdentifier "c") (ENumber "1")) ])
           (EIdentifier "n")
       , ESymbol Ord "\8943"
       , ESub
           (EDelimited
              "(" ")" [ Right (ESub (EIdentifier "c") (EIdentifier "q")) ])
           (EIdentifier "n")
       ])
, EFraction
    NormalFrac
    (ESuper (EIdentifier "z") (EIdentifier "n"))
    (EGrouped [ EIdentifier "n" , ESymbol Ord "!" ])
]
>>> typst
zws_p F_q lr((a_1 comma dots.h comma a_p semi c_1 comma dots.h comma c_q semi z)) eq sum_(n eq 0)^oo frac(lr((a_1))_n dots.h.c lr((a_p))_n, lr((c_1))_n dots.h.c lr((c_q))_n) frac(z^n, n excl)