I am simply trying to plot three different for loops. 

> a[0] := 100;
> r := 2;
> for n to 10 do a[n] := r a[n-1]) end do;

> b[0] := 100;
> r := .5;                            
> for n to 10 do b[n] := r b[n-1]) end do;

> c[0] := 100;
> r := -1;
> for n to 10 do c[n] := r c[n-1]) end do;

The loops are calculating...