Let f(x)=∑n=0∞anxnf(x) = \sum_{n=0}^{\infty} a_n x^nf(x)=∑n=0∞anxn with ana_nan periodic with period 333, where a0=1,a1=2,a2=3a_0=1, a_1=2, a_2=3a0=1,a1=2,a2=3. What is f(x)f(x)f(x)?
1+2x+3x21−x3\frac{1+2x+3x^2}{1-x^3}1−x31+2x+3x2
1+2x+3x21+x3\frac{1+2x+3x^2}{1+x^3}1+x31+2x+3x2
1+2x+3x21−x\frac{1+2x+3x^2}{1-x}1−x1+2x+3x2
1+2x+3x2+x3+…1+2x+3x^2+x^3+\dots1+2x+3x2+x3+…