Had to dig deep to find this for you but laid up at the moment so not a problem. I remember on a This Old house project they went to a awesome stair case manuf. in wisconsin. These guys are awesome. Here you go. www.arcways.com
I only know how I'd build it to pour with concrete.
First I would shore up a deck. The decking would be of multible layers of 1/2" or even 1/4" plywood. Then I would form the sides, again with multiple layers of thin plywood.
After forming up the bottom and sides, I would use simple math to determine the run and rise. But it would require physical measurements rather than thoeretical run and rise. The rise is a constant, but your run would have to be measured on both the inside and outside stringer sides, not on paper, but actually measuring the work in place. Then the math would involve dividing up the diagonal stringer against the risers, within code.
If you want a CAD design, give me the rise and other pertinent dimensions, and I may be able to give you a drawing. But that may require me being nice to my son, which is hard to do as the acorn falls not far from the tree.
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