DirectoryQ (Built-in Mathematica Symbol)

DirectoryQ["name"] gives True if the directory with the specified name exists, and gives False otherwise.

DirectoryStack (Built-in Mathematica Symbol)

DirectoryStack[] gives the directory stack that represents the sequence of current directories used.

DirichletCharacter (Built-in Mathematica Symbol)

DirichletCharacter[k, j, n] gives the Dirichlet character \[Chi] {k, j} (n) with modulus k and index j.

DirichletConvolve (Built-in Mathematica Symbol)

DirichletConvolve[f, g, n, m] gives the Dirichlet convolution of the expressions f and g.

DirichletDistribution (Built-in Mathematica Symbol)

DirichletDistribution[{\[Alpha]_1, ..., \[Alpha] k +1}] represents a Dirichlet distribution of dimension k with shape parameters \[Alpha]_i.

DirichletL (Built-in Mathematica Symbol)

DirichletL[k, j, s] gives the Dirichlet L-function L(\[Chi], s) for the Dirichlet character \[Chi](n) with modulus k and index j.

DirichletTransform (Built-in Mathematica Symbol)

DirichletTransform[expr, n, s] gives the Dirichlet transform of expr with respect to n.

DiscreteConvolve (Built-in Mathematica Symbol)

DiscreteConvolve[f, g, n, m] gives the convolution with respect to n of the expressions f and g. DiscreteConvolve[f, g, {n_1, n_2, ...}, {m_1, m_2, ...}] gives the ...

DiscreteDelta (Built-in Mathematica Symbol)

DiscreteDelta[n_1, n_2, ...] gives the discrete delta function \[Delta] (n_1, n_2, ...), equal to 1 if all the n_i are zero, and 0 otherwise.

DiscreteIndicator (Built-in Mathematica Symbol)

DiscreteIndicator[x, x_1, {u_1, u_2, ...}] yields the discrete indicator function, equal to 1 if x = x_1 and 0 if x = u_i for any i.