Let f(x)=ex=∑n=0∞xnn!f(x) = e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!}f(x)=ex=∑n=0∞n!xn. What is the coefficient of x3x^3x3 in the power series for f(x)2=e2xf(x)^2 = e^{2x}f(x)2=e2x?
13\frac{1}{3}31
23\frac{2}{3}32
43\frac{4}{3}34
83\frac{8}{3}38