[irchans]

I get that the probability of flopping a 4-flush or a flush with 87s is

3* 11/50 10/49 * (52 - 13)/48 + 11/50 *10/49 * 9/48
= 0.117857.

For the probability of flopping an open ended 4-straight or
a straight I get

(4^3 + 4^2*(52 - 20)*3 + 2*4*6*3 + 4^2*2*3*3) / b[50,3]
= 0.103673

where b[x,y] = x!/y!/(x-y)!

These computations are tricky so don't believe these numbers until someone else verifies them.