// -1 + n \
|| / p \ |
||p*|1 - ------| |
|| \ -1 + p/ / / | p | \ /| p | \ / | p | \\|
||-------------------- for Or|And|-1 + re(n) <= -1, |------| < 1|, And||------| <= 1, -1 + re(n) > 0|, And|-1 + re(n) <= 0, |------| <= 1, -1 + re(n) > -1|||
|| (1 - p)*Gamma(n) \ \ |-1 + p| / \|-1 + p| / \ |-1 + p| //|
|| |
n || oo |
z*(1 - p) *n!*|<____ |
||\ ` |
|| \ k -k |
|| \ k*p *(1 - p) |
|| / -------------- otherwise |
|| / k!*(n - k)! |
||/___, |
||k = 0 |
\\ /
$$z \left(1 - p\right)^{n} \left(\begin{cases} \frac{p \left(- \frac{p}{p - 1} + 1\right)^{n - 1}}{\left(1 - p\right) \Gamma\left(n\right)} & \text{for}\: \left(\operatorname{re}{\left(n\right)} - 1 \leq -1 \wedge \left|{\frac{p}{p - 1}}\right| < 1\right) \vee \left(\left|{\frac{p}{p - 1}}\right| \leq 1 \wedge \operatorname{re}{\left(n\right)} - 1 > 0\right) \vee \left(\operatorname{re}{\left(n\right)} - 1 \leq 0 \wedge \left|{\frac{p}{p - 1}}\right| \leq 1 \wedge \operatorname{re}{\left(n\right)} - 1 > -1\right) \\\sum_{k=0}^{\infty} \frac{k p^{k} \left(1 - p\right)^{- k}}{k! \left(- k + n\right)!} & \text{otherwise} \end{cases}\right) n!$$
z*(1 - p)^n*factorial(n)*Piecewise((p*(1 - p/(-1 + p))^(-1 + n)/((1 - p)*gamma(n)), ((-1 + re(n) <= -1)∧(Abs(p/(-1 + p)) < 1))∨((-1 + re(n) > 0)∧(Abs(p/(-1 + p)) <= 1))∨((-1 + re(n) <= 0)∧(-1 + re(n) > -1)∧(Abs(p/(-1 + p)) <= 1))), (Sum(k*p^k*(1 - p)^(-k)/(factorial(k)*factorial(n - k)), (k, 0, oo)), True))