ok, if we start with an equal triangle number 1 with short sides 2m. Then the long side is 2.8m. That then becomes one of triangle number 2's short sides.so triangle number 2s long side is 4m. that then becomes a side for triangle number 3, etc etc.that creates a spiral made of triangles that increase in size in relation to the previous triangle. (I've rounded the math up a bit).

using what you put above, the closest I can get right now is (using a,b,and c )

c[n]=c[n-a+b]

but that only looks to be part of it.