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 |[The Devil and the Coin Flip Game](https://github.com/norvig/pytudes/blob/master/ipynb/Coin%20Flip.ipynb)<br>*How to beat the Devil at his own game.*|
 |[Translating English Sentences into Propositional Logic Statements](https://github.com/norvig/pytudes/blob/master/ipynb/PropositionalLogic.ipynb)<br>*Automatically converting informal English sentences into formal Propositional Logic.*|
 |[The Puzzle of the Misanthropic Neighbors](https://github.com/norvig/pytudes/blob/master/ipynb/Mean%20Misanthrope%20Density.ipynb)<br>*How crowded will this neighborhood be, if nobody wants to live next door to anyone else?*|
-|[Countdown to 2016](https://github.com/norvig/pytudes/blob/master/ipynb/Countdown.ipynb)<br>*Solving the equation 10 _ 9 _ 8 _ 7 _ 6 _ 5 _ 4 _ 3 _ 2 _ 1 = 2016. From an Alex Bellos puzzle.*|
+|[Four 4s, Five 5s, and Countdown to 2016](https://github.com/norvig/pytudes/blob/master/ipynb/Countdown.ipynb)<br>*Solving the equation 10 _ 9 _ 8 _ 7 _ 6 _ 5 _ 4 _ 3 _ 2 _ 1 = 2016. From an Alex Bellos puzzle.*|
 |[Sicherman Dice](https://github.com/norvig/pytudes/blob/master/ipynb/Sicherman%20Dice.ipynb)<br>*Find a pair of dice that is like a regular pair of dice, only different.*|
 |[Beal's Conjecture Revisited](https://github.com/norvig/pytudes/blob/master/ipynb/Beal.ipynb)<br>*A search for counterexamples to Beal's Conjecture*|
 |[When is Cheryl's Birthday?](https://github.com/norvig/pytudes/blob/master/ipynb/Cheryl.ipynb)<br>*Solving the "Cheryl's Birthday" logic puzzle.*|