Dr. David Kirkby wrote: > 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. >
Wow, that seems totally ambiguous. Is 5!!! equal to (5!!)! or (5!)!! or ((5!)!)! The notation is pretty bad in this case. However note that: In[1]:= 5! ! Out[1]= 668950291344912705758811805409037258675274633313802981029567135230163\ > 355724496298936687416527198498130815763789321409055253440858940812185989\ > 8481114389650005964960521256960000000000000000000000000000 (note the space between the exclamation points) Jason -- Jason Grout --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
