You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(4aS,6S,7aR)-6-(pyridin-4-ylmethoxymethyl)-3,4a,5,6,7,7a-hexahydro-2H-cyclopenta[b][1,4]oxazin-4-yl]-2-(1-methylpyrazol-3-yl)ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H26N4O3
assistant