Ummm, you got that backwards. A 12MP Bayer array requires three sensor pixels for each image pixel, one pixel for red, one pixel for green, and one pixel for blue. A Foveon sensor requires one sensor pixel for each image pixel, because a Foveon sensor can detect all three colors at each pixel. So a camera with a Bayer 12M pixel sensor generates a 4MP image resolution.
I have a Nikon D7000 16M pixel camera which outputs images at 4928 x 3263 pixels. Multiply that and as expected you get 16 million.
I also have a Sigma DP1 14M pixel Foveon sensor camera which outputs images at 2640 x 1760 pixels which gets you 4.69 million. (14 divided by three).
Looks right to me.