You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named tert-butyl 8,11,15,18-tetrazatetracyclo[8.8.0.02,7.012,18]octadeca-1(10),2,4,6,8,11-hexaene-15-carboxylate;ethane by IUPAC nomenclature, provide its molecular formula.
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C21H28N4O2
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