Question: For an application we are working on I need to generate sample credit card numbers which pass the Luhn algorithm but which are also unique, so we cannot use the sample credit card numbers.

We need to be able to generate around 300 card numbers at a time, and ideally i would be able to do this when generating my input data.

Many Thanks

Answer: 
Create random numbers, then calculate the checksum number.

You can find more information at [Wikipedia - Luhn](http://en.wikipedia.org/wiki/Luhn), both details about the algorithm and links to different implementations.
If you need a list to test each card, you'll find one here. [How to test credit card interactions?](https://stackoverflow.com/questions/66880/how-to-test-credit-card-interactions/66988#66988)