Compute the value V(n,k), needed to caclulate the eppf of a Finite Dirichlet process when the prior on the component-weigts of the mixture is a Dirichlet with parameter gamma (i.e. when unnormailized weights are distributed as Gamma(,1) ) when the number of component are fixed to M^*, i.e. a Dirac prior assigning mass only to M^* is assumed. See Section 9.1.1 of the Paper Argiento de Iorio 2019 for more details.