Right. The number of pops must be a positive integer power of 2 for 1-stop increases.
2^1 = 2 pops for +1 stop
2^2 = 4 pops for +2 stops
2^3 = 8 pops for +3 stops…and so forth.
In general, we need 2^n pops for +n stops of exposure increase using multi-pop flash exposures of equal strength.