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-O-benzyl 5-O,5-O'-dimethyl (4aR,7aR)-7-methylidene-2,3,4,4a,6,7a-hexahydrocyclopenta[b]pyridine-1,5,5-tricarboxylate by IUPAC nomenclature, provide its molecular formula.
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C21H25NO6
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