Why Today is Math Geeks’ Favorite Friday the 13th in a Century

Well, hello there! It’s been a while. A lot has happened since we’ve seen each other, and we have a mid-game (ish) recap coming your way next week. But today, let’s take a moment to celebrate a rare moment of true mathematical predictability written by Harvard Economist Scott Kominers. In a world filled with uncertainty, it’s nice to know we’ll have something to look forward to in the year 2102. We’ll see you next week with more from The Prediction Game!

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For most people, Friday the 13th conjures images of bad luck and cheesy horror films. But in the math circles I run in, this particular Friday the 13th presents a rare and “golden” opportunity.

The date, 8-13-21, combines three adjacent numbers in the Fibonacci sequence – a renowned mathematical progression obtained by starting with 1 and 1, and then successively adding the prior two numbers to get the next one:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597…

It’s not often we see dates that line up with this sequence. The last time this happened was May 8th, 2013, and I guess if you’re willing to stretch, then you could claim May 5th, 1989 as a candidate (55, 89). But I think we’d all agree after scanning the numbers above that dates like today are few and far between.