Negative Binomial Series∑j=0∞(j+k−1k−1)aj=(1−a)−k if ∣a∣<1\sum\limits_{j=0}^{\infty} {{j+k-1} \choose {k-1}} a^j = (1-a)^{-k} ~\text{if}~ |a| < 1j=0∑∞(k−1j+k−1)aj=(1−a)−k if ∣a∣<1
