2. g : {2..k
}
3. x : {2..k
}
4. y : {2..k
}
5. x
y<k
6. x<y
7. x<x
y
8. y<x
y
9. h : {2..k
}
10. h = split_factor2(g; x; y)
11. h(x
y) = 0
12. h(x) = g(x)+g(x
y)
13. h(y) = g(y)+g(x
y)
14.
u:{2..k}. 
u = x 
u = y u = xy h(u) = g(u)
{x+1..y}(g) = {x+1..y}(h)
