You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 1-(2,3-dihydro-1H-inden-1-yl)-4-(3-propan-2-yl-1,2,4-oxadiazol-5-yl)pyrrolidin-2-one by IUPAC nomenclature, provide its molecular formula.
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C18H21N3O2
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