Look and Say Day - December 11

Happy Look and Say Day! It celebrates an especially tricky sequence of numbers, the Look and Say Sequence.

Look and Say Day is about the following sequence of numbers:

1

11

21

1211

111221

312211

13112221

etc

Simply seeing this sequence, the average person probably wouldn't figure out the next numbers (1113213211 and 31131211131221, FWIW) ... but since I told you this is Look and Say Day, you may have already figured it out. Starting with a "seed number" of 1, each subsequent number is basically the pronunciation of like digits:

1

(one 1)

11

(two 1s)

21 

(one 2, two 1s)

1211 

(one 1, one 2, two 1s)

111221

(three 1s, two 2s, one 1)

312211

This turns out to be a fairly easy (if lengthy) sequence to derive. (It might be one of those puzzles that a child is more likely to resolve than an adult, since they'll spend less time going down incorrect paths.) There's a video on the Look and Say Sequence here.

We celebrate Look and Say Day on December 11 (or 12/11) because 1211 is the largest number in the sequence that looks like a date.