Other posters are probably correct...there are may be spaces mixed in with the tabs. Try doing the search & replace to replace all the tabs with a few spaces.
Try as below :
def Factorial(n): # Return the factorial
myresult = 1
for j in range (1,n):
myresult = myresult * j
print "The factorial is: ",myresult
Sublime Text users:
Sublime Text to use tabs for your indentation:
Convert Indentation to Tabs
Indent Using Spaces option as well in a same sub-menu above. This will immediately fix your issue.
To easily check for the problems with your tabs/spaces you can actually do as below:
python -m tabnanny yourfile.py
Or you can just set up the editor correctly of course.
I hope the above given solutions will help you in resolving your all of the errors.