Calculating a subnet address

[Dist]

Does anyone know a formula for working out the address of a subnet within a large range of subnets? For example, if i have a class A IP and subnet it into 2048 subnets, whats the address of subnet X?

I can work it out myself, but i don't have a good way of explaining my method, so would like to know a formula to work it out (taking into account that subnet 0 would be the 1st subnet).

 

[Dist]

What i am looking for is something i can do with a pen, paper and calculator. Its simple to work out for example the 4th subnet in the 192.168.0.0/27 network, but working out the 210th subnet in the 10.0.0.0/19 subnet is a little more complex.

 

[Dist]

Great thats just what i was after, thankyou.

One more question, when using that method should i be searching for exactly the subnet i want, or 1 less then the subnet i want? I ask because 10.0.0.0 would be subnet 1, 10.0.32.0 subnet 2 etc... so because counting starts at 0 should i subtract 1 from the subnet i am after?