Halting
 
   
  
  You can also solve the Goldbach Conjecture, for the special case of only considering numbers arising before you beat the machine with a stick.
Comics by Zach Weinersmith, transcribed by the crowd*, finally searchable on the webs!
*well, just me… 
   
  
  You can also solve the Goldbach Conjecture, for the special case of only considering numbers arising before you beat the machine with a stick.