Fuente TeX:

H(X_1,...,X_n) = -\sum_{x_1 \in \mathcal{X}} ... \sum_{x_n \in \mathcal{X}} P(X_1=x_1 ... X_n=x_n) log\left(P(X_1=x_1 ... X_n=x_n)\right) = -\sum_{i \in \mathcal{X}}\sum_{j \in \mathcal{X}} P(X_1=i)P(X_2=j | X_1=i)^{n-1} log\left(P(X_1=i)P(X_2=j | X_1=i)^{n-1}\right) = -\sum_{i \in \mathcal{X}}\sum_{j \in \mathcal{X}} \pi_i P_{ij}^{n-1} log\left(\pi_i P_{ij}^{n-1}\right)