How about this, everyone . . .. . 2 coils result in 1/2 the resistance. 3 coils result in 1/3 x Ω. 4 coils result in 1/4 x Ω. (I'm starting to see a pattern there.)
There are no setups with coils in series, unless you're vaping two devices at once. In series, each coil is an individual function, and has it's own resistance.