I am trying to execute some instructions containing for loops and variables in sranges. The instructions are simple; yet I keep getting an error message and can't figure out where the error is. My program is at https://cloud.sagemath.com/projects/f9c3371c-3682-4811-b236-f62976d8fa24/files/scratch.sagews. I am trying to use this simple program to see if I have correctly executed a much larger program.