[Guthrie]

Back in the seventies I read Thorpe's book on blackjack and decided to test his theories by writing a blackjack simulator. I had access to an IBM 1130 so I taught myself FORTRAN and set to work. Writing a random number generator was beyond my skill level, and I figured that no human really shuffled randomly anyway, so I decided to write a subroutine that actually shuffled the deck. I figured a good dealer would cut the deck exactly in half and drop one card off each side, then cut exactly in half and do it again, and so on. I started with the cards ordered like a new deck fresh from the factory, and had a single input, how many times to shuffle. I told it to shuffle eight times, as I recall, and nothing happened. The deck was completely unchanged. I spent days trying to debug the thing, then picked up a new deck of cards and very carefully recreated the shuffle one card at a time. As you have probably guessed by now, the subroutine was working perfectly, but after eight times (or whatever the number was), the deck was back in its original order. There were also some very interesting combinations along the way.