I know that game as "nim," and Wikipedia shows 21 as a variation. https://en.wikipedia.org/wiki/Nim#The_21_game https://en.wikipedia.org/wiki/Nim#The_21_game T

I know that game as "nim," and Wikipedia shows 21 as a variation. https://en.wikipedia.org/wiki/Nim#The_21_game https://en.wikipedia.org/wiki/Nim#The_21_game There's a mechanical version of an AI from the 60s called Dr. Nim. It doesn't learn to play, of course, but instead it has a 3-bit binary counter.