What is the coefficient of x6x^6x6 in the Maclaurin series for f(x)=e−x2f(x) = e^{-x^2}f(x)=e−x2?
16\frac{1}{6}61
−16-\frac{1}{6}−61
1720\frac{1}{720}7201
−1720-\frac{1}{720}−7201