// 2 \
// x \ || x | 2| |
|| ----- for |x| < 1| || ------ for |x | < 1|
|| 1 - x | || 2 |
|| | || 1 - x |
|| oo | || |
|< ___ | + |< oo |
|| \ ` | || ___ |
|| \ n | || \ ` |
|| / x otherwise | || \ 2*n |
|| /__, | || / x otherwise |
\\n = 1 / || /__, |
\\n = 1 /
$$\begin{cases} \frac{x}{1 - x} & \text{for}\: \left|{x}\right| < 1 \\\sum_{n=1}^{\infty} x^{n} & \text{otherwise} \end{cases} + \begin{cases} \frac{x^{2}}{1 - x^{2}} & \text{for}\: \left|{x^{2}}\right| < 1 \\\sum_{n=1}^{\infty} x^{2 n} & \text{otherwise} \end{cases}$$
Piecewise((x/(1 - x), |x| < 1), (Sum(x^n, (n, 1, oo)), True)) + Piecewise((x^2/(1 - x^2), |x^2| < 1), (Sum(x^(2*n), (n, 1, oo)), True))