/ / ___ ___\
| ___ ___ |\/ 3 *\/ x |
|\/ 3 *\/ x *atanh|-----------|
| \ 3 /
|------------------------------ for And(x >= -3, x < 3)
| 3
|
| oo
< ____
| \ `
| \ -n n
| \ 3 *x
| / -------- otherwise
| / -1 + 2*n
| /___,
| n = 1
\
$$\begin{cases} \frac{\sqrt{3} \sqrt{x} \operatorname{atanh}{\left(\frac{\sqrt{3} \sqrt{x}}{3} \right)}}{3} & \text{for}\: x \geq -3 \wedge x < 3 \\\sum_{n=1}^{\infty} \frac{3^{- n} x^{n}}{2 n - 1} & \text{otherwise} \end{cases}$$
Piecewise((sqrt(3)*sqrt(x)*atanh(sqrt(3)*sqrt(x)/3)/3, (x >= -3)∧(x < 3)), (Sum(3^(-n)*x^n/(-1 + 2*n), (n, 1, oo)), True))