You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 2-(8a-ethyl-3-oxo-1,5,6,8-tetrahydro-[1,3]oxazolo[3,4-a]pyrazin-7-yl)-6,7-dihydro-5H-cyclopenta[b]pyridine-3-carboxylic acid by IUPAC nomenclature, provide its molecular formula.
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C17H21N3O4
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