What do two adjacent pound signs mean in a C macro?

Question

I\'m taking a look at an application that defines a large set of constant arrays. What really confuses me is the use of two pound signs next to each other in a macro. For ex

Answer 1

Als and sepp2k give correct answer.

However I would like to add, that this macro seems to be completely unnecessary.

unsigned int value = r0(b,e,a,f);

can be replaced by better and shorter:

unsigned int value = 0xbeaf;