Binomial coefficient
From specialfunctionswiki
The binomial coefficients are defined by the formula $${n \choose k} = \dfrac{n!}{(n-k)!k!}.$$
Properties
Theorem (Binomial Theorem): $(a+b)^n = \displaystyle\sum_{k=0}^n {n \choose k} a^k b^{n-k}$
Proof: █
