You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named trimethyl-[2-[(8-oxo-16-azatetracyclo[7.7.1.02,7.013,17]heptadeca-1(16),2,4,6,9,11,13(17),14-octaen-14-yl)oxy]ethyl]azanium;iodide by IUPAC nomenclature, provide its molecular formula.
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C21H21IN2O2
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