-> I heard they were doing the Tower of Hanoi puzzle with 64 disks. I  
-> don't know how many moves that takes, but I'm sure it's a lot more than  
-> nine billion. M(n) = 2*M(n-1)+1. M(1) = 1. So what's M(64)?  
  
Answer: A bit more than 1.8 x 10^19. 
  
That's more than four billion *squared*! 
  
If a computer simulates the puzzle at 1000 moves per second, it will 
take 1.8e16 seconds to finish. That's about 57 billion years. Several 
times the present "age of the universe", since the Big Bang. 
  
                        dow 
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