  For each pair of positive integers (k,r) such that k+1,r-1 are coprime, we
introduce an ideal $I^{(k,r)}_n$ of the ring of symmetric polynomials. The
ideal $I^{(k,r)}_n$ has a basis consisting of Jack polynomials with parameter
$\beta=-(r-1)/(k+1)$, and admits an action of a family of differential
operators of Dunkl type including the positive half of the Virasoro algebra.
The space $I^{(k,2)}_n$ coincides with the space of all symmetric polynomials
in $n$ variables which vanish when $k+1$ variables are set equal. The space
$I_n^{(2,r)}$ coincides with the space of correlation functions of an abelian
current of a vertex operator algebra related to Virasoro minimal series
(3,r+2).
