Dave Brubeck messes with time

Kelley deal (sister of Kim) wrote a song with normal time signature but with this crazy clapping pattern in the background. I suspect it may be a kids’ game or something. Took me a few minutes to figure out the pattern but it goes 1-1 2-1 2 3-1 2 3 4-1 2 3-1 2- etc
Kinda fun to clap along once you figure it out.