<math> <apply><forall/> <bvar><ci>n</ci></bvar> <condition><apply><gt/><ci>n</ci><cn>0</cn></apply></condition> <apply><eq/> <apply><factorial/><ci>n</ci></apply> <apply><times/> <ci>n</ci> <apply><factorial/> <apply><minus/><ci>n</ci><cn>1</cn></apply> </apply> </apply> </apply> </apply> </math>