You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 1-[(1S)-1-hydroxy-2-methylpyrrolidin-1-ium-1-yl]-2-[(2R)-5-nitro-2,3-dihydro-1H-inden-2-yl]ethanone is given. What is its corresponding molecular formula?
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C16H21N2O4+
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