I assumed it was a riff off of the millennium prize problems (which do have a bounty of $1M each), as a way of saying "here are some other very interesting unso

I assumed it was a riff off of the millennium prize problems (which do have a bounty of $1M each), as a way of saying "here are some other very interesting unsolved problems" http://www.claymath.org/millennium-problems/millennium-prize-problems http://www.claymath.org/millennium-problems/millennium-prize...