You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 5-chloro-N-[2-(4-ethoxyphenyl)ethyl]-9-oxa-1-azatricyclo[6.3.1.04,12]dodeca-2,4,6,8(12)-tetraene-2-carboxamide by IUPAC nomenclature, provide its molecular formula.
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C21H21ClN2O3
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