Just going to post that this is inaccurate.
1,073,741,824 is just over 1 billion (not trillion).
Second, the calculations you posted for all of your calculations assume that if you are looking for a 2 IV Pokemon there are only 2 stats. There are 15 possible combinations of 2 IVs existing. That means that there are 13,852,815 possible combinations out of the 1,073,741,824
So about 1 in 78 to get a 2 IV Pokemon.
Now you just need to remember that these are the "binary" (maxed or not maxed) possibilities.
1 outcome for zero IVs
6 outcomes for 1 IV
15 outcomes for 2 IVs
20 outcomes for 3 IVs
15 for 4 IVs
6 for 5 IVs
1 for 6 IVs
Aside from the 6 IVs scenario, you just need to use
z=x*31^y
where
x = the number of binary combinations for desired IVs
y = 6 - number of maxed IVs desired.
You're chances are z/32^6
The guy above me, Le Scraf, the chance for a 0 IV Pokemon is only
1 in 1,073,741,824