Donald Knuth's Christmas pi surprise

Jon Cog writes, "For Christmas, mathematician Donald Knuth shared some great geeky fun. He revealed how for the last 57 years, he's been incorporating the digits of pi into the exercises of his computer programming books -- a whopping 1,700 times. And before long his annual 'Christmas Tree' lecture 'had turned into a kind of intellectual funhouse,' sharing other mind-boggling pi-related miscellanies."

For example, one author wrote an entire book where each word has exactly the number of letters as its corresponding digit in pi. (Soon that book devolves into some bizarre poetry, a science-fiction screenplay called the Zompyr Chronicle, and then a crossword puzzle.) Knuth himself also created a Sudoku puzzle in which the filled-in 'clue' numbers are, in order, the first 32 digits of pi. Other mathematicians have worked the digits of pi into even more exotic KenKen, Kakuro, and Hidato puzzles. And pi even managed to work its way into the solution of one puzzle that was entirely visual, involving only lines that connect the dots on a grid.

The puzzle-maker had designed the puzzle so that the line connecting all the dots drew a lovely and unmistakable picture -- of the mathematical symbol for pi.

And after revealing it to his astonished audience, Knuth shouted out 'Merry Christmas!'

Donald Knuth’s 2019 ‘Christmas Tree Lecture’ Explores Pi in ‘The Art of Computer Programming’ [David Cassel/The New Stack]

(Thanks, Jon Cog!)