[BruceZ]

For example, here are the first 3 terms, which give an accuracy to much better than 0.04%. This assumes you don't hold a J-A:

9*24/C(50,2) -
C(9,2)*24*19/C(50,2)/C(48,2) +
C(9,3)*24*(18*14 + 1*18)/C(50,2)/C(48,2)/C(46,2)

=~ 16.5%