If output="vector", this function returns a named vector.
This vector is made of the non-zero (i.e. positive) Kostka numbers
\(K(\lambda,\mu)\), which are integers, and its names encode the
partitions \(\mu\).
If output="list", this function returns a list of lists.
Each of these lists has two
elements. The first one is named mu and is an integer
partition, and the second one is named value and is a positive
integer, the Kostka number \(K(\lambda,\mu)\). It is faster to
compute the Kostka numbers with this function than computing the
individual Kostka numbers with the function KostkaNumber.