B(a, b) = _{(0, 1)} u^{a}^{ - 1}(1 - u)^{b-1 }du.

B(a, b) = gam(a) gam(b) / gam(a + b).

B(j, k) = (j - 1)!(k - 1)! / (j + k -1)!

f(u) = u^{a} - 1 (1 - u)^{b - 1} / B(a, b), 0 < u < 1

F_{p}(k - 1) = G_{k}(1 - p)

E(U^{k}) = B(a + k, b) / B(a, b).

U = (m / n)X / [1 + (m / n)X]