This article doesn't say so I don't know.
There are more than one, D3 and D6 mainly.
As supplement, I'm familiar with D2 and D3. D2 used to be the common supplement but has been replaced by D3 as D3 is the form we make naturally and is so thought to be better utilized. I recently posted something with the opinion that D2 may be as beneficial as D3.
That summarizes my readings on the matter.
Tried to edit my incorrect response in post #7. This info, even speculation, is great. Bump.