You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (7R,8aR)-7-[(6-methylpyridin-2-yl)methoxy]-2-(pyridin-3-ylmethyl)-3,4,6,7,8,8a-hexahydro-1H-pyrrolo[1,2-a]pyrazine by IUPAC nomenclature, provide its molecular formula.
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C20H26N4O
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