I can''t find a better name. It seems the function can be used to build Fermionic Galerkin matrices.
Nice recursive algorithm! You might be interested in my implementation for nchoose2: http://www.mathworks.com/matlabcentral/fileexchange/20144-nchoose2-v2-1-jun-2008
There is no mention of the need for MERGESA other than the error message I see when trying to run the file.
Other than that, this is a nice recursive solution to the combinations without replacement problem.
FEX requirement (try again)
Add MERGESA (FEX #28930) in the requirement