There are a lot of algorithms which seem to have been supplied an official number, such as Algorithm 76, Hierarchical clustering using the minimum spanning tree. Another example is Algorithm 123, Single Transferable Vote by Meek's Method. These numbers seem to refer to some official registry, but I haven't been able to find out what this registry is or how numbers are assigned. It does not seem to be related to the journal publishing the algorithm. Does anyone know how this system works and where one can read more about it?