:f[x_0,\ldots,x_n] = \frac{1}{n!} \int_{x_0}^{x_n} f^{(n)}(t)B_{n-1}(t) \, dt
:f[x_0,\ldots,x_n]
:\frac{1}{n!}
:\int_{x_0}^{x_n}
:f^{(n)}(t)B_{n-1}(t) dt \,
:\lim_{n\rightarrow\infty}\sum_{i=0}^n \frac{1}{i}