Bill,
coils in series get added, coils in parallel are treated like parallel resistorsL1 x L2 = Lx
L1 + L2 = Ly
Lx and Ly then divide up, just like odd value resistors.
Bill, remember that coils in series will also add DCR, and orientation of the coils may interact also.
I have never had reason to parallel coils as interaction would mess with that also.
What value do you need????? I can look in the basement inventory and check for you.
If you have a coil that is a higher value than what you need, then remove a few turns and measure until the value you want is reached.
Wayne, double check my work above so I don't give wrong info...
Ron