Dr. David Kirkby wrote: > Em, I thought I'd try this in Mathematica > > In[1]:= 5! > > Out[1]= 120 > > In[2]:= 5!! > > Out[2]= 15 > > In[3]:= 5!!! > > Out[3]= 1307674368000 > > In[4]:= 5!!!! > > Out[4]= 2027025 > > In[5]:= 5!!!!! > <spends a long time doing whatever it is trying to compute. > > > > Anyone like to guess what it's doing?
Trying this in Wolfram Alpha http://www.wolframalpha.com/input/?i=5%21%21 reveals what Mathematica is doing. Apparently n!! is the double factorial http://reference.wolfram.com/mathematica/ref/Factorial2.html n!! = nx(n-2)x(n-2)x... As a non-mathematician I'd never herd of such a thing myself. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
