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 2-(1-benzyl-2-oxo-5,6,7,7a-tetrahydro-4H-indol-3-yl)-N-propan-2-ylacetamide is given. What is its corresponding molecular formula?
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C20H26N2O2
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