diff --git a/README.md b/README.md
index d8e1dc8..be030d0 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,7 @@ Some programs are in Jupyter (`.ipynb`) notebooks, some in `.py` files. For each
 |Run|Year|Logic and Number Puzzles|
 |---|----|---|
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Cryptarithmetic.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCryptarithmetic.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCryptarithmetic.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Cryptarithmetic.ipynb) | 2014 | <b><a href="ipynb/Cryptarithmetic.ipynb" title="Substitute digits for letters and make NUM + BER = PLAY">Cryptarithmetic</a></b> |
-| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/equilength-numbers.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fequilength-numbers.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fequilength-numbers.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/equilength-numbers.ipynb) | 2020 | <b><a href="ipynb/equilength-numbers.ipynb" title=""Four" has 4 letters, and "two plus nine" has 11. What other expressions are like this?">Equilength Number Expressions</a></b> |
+| [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/equilength-numbers.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2Fequilength-numbers.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2Fequilength-numbers.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/equilength-numbers.ipynb) | 2020 | <b><a href="ipynb/equilength-numbers.ipynb" title="'Four' has 4 letters, and 'two plus nine' has 11. What other expressions are like this?">Equilength Number Expressions</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FCountdown.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FCountdown.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Countdown.ipynb) | 2020 | <b><a href="ipynb/Countdown.ipynb" title="Solving the equation 10 _ 9 _ 8 _ 7 _ 6 _ 5 _ 4 _ 3 _ 2 _ 1 = 2016 and other similar puzzles.">Making Numbers: Four 4s, Five 5s, and Countdowns</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Socks.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FSocks.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FSocks.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Socks.ipynb) | 2019 | <b><a href="ipynb/Socks.ipynb" title="What is the probability that you will be able to pair up socks as you randomly pull them out of the dryer?">Pairing Socks</a></b> |
 | [c](https://colab.research.google.com/github/norvig/pytudes/blob/master/ipynb/Sicherman%20Dice.ipynb) [d](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FSicherman%20Dice.ipynb)  [m](https://mybinder.org/v2/gh/norvig/pytudes/master?filepath=ipynb%2FSicherman%20Dice.ipynb) [n](https://nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Sicherman%20Dice.ipynb) | 2018 | <b><a href="ipynb/Sicherman%20Dice.ipynb" title="Find a pair of dice that is like a regular pair of dice, only different">Sicherman Dice</a></b> |