A(z)=∑n≥0an∗zn{\displaystyle A(z)=\sum _{n\geq 0}{a_{n}*z^{n}}}
A(z)+A(−z)2=12∗(∑n≥0an∗zn+∑n≥0an∗(−z)n){\displaystyle {\frac {A(z)+A(-z)}{2}}={\frac {1}{2}}*(\sum _{n\geq 0}{a_{n}*z^{n}}+\sum _{n\geq 0}{a_{n}*(-z)^{n}})}
=> Ungerade z fallen weg
∑n≥0a2n∗z2n{\displaystyle \sum _{n\geq 0}{a_{2n}*z^{2n}}}
